O/W/O type multiple emulsion and method of preparing the same

ABSTRACT

This invention relates to an oil-in-water-in-oil (O/W/O) type multiple emulsion which contains an inner oil phase, a water phase, and an outer oil phase. The inner oil phase is first dispersed in water to form an oil-in-water (O/W) emulsion. Then, the O/W emulsion is further dispersed in the outer oil phase to form the O/W/O type multiple emulsion. The outer oil phase contains an organophilic clay mineral, which can effectively prevent the inter-mixing of the inner oil phase with the outer oil phase, thus, producing an O/W/O type multiple emulsion with excellent storage stability. Upon the using of an oil-soluble compound in the inner oil phase, this multiple emulsion system can prevent the oil-soluble compound from being oxidized. In addition, since different kinds of oils can be selected for the making of the inner and outer oil phases, respectively, the O/W/O type multiple emulsion system allows one to present two different kinds of oils, which have different properties independent from each other, in one emulsion system.

RELATED APPLICATIONS

This application claims the priority of Japanese Patent Application No.7-347770 filed on Dec. 14, 1995, 8-32949 filed on Jan. 26, 1996, 8-50833filed on Feb. 13, 1996, 8-99244 filed on Mar. 28, 1996, 8-175711 filedon Jun. 14, 1996, and 8-205428 filed on Jul. 15, 1996 which areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an O/W/O type multiple emulsion and amethod of making the same and, in particular, to prevention of its inneroil phase and outer oil phase from combining together and further toimprovement in stabilization of oil-soluble agents blended in the inneroil phase.

BACKGROUND OF THE INVENTION

Oil-in-water-in-oil type (referred to as "O/W/O type" in the following)emulsion composition in which an oil-in-water type (referred to as "O/Wtype" in the following) emulsion is further emulsified and dispersed inan oil phase, also known as complex emulsion or multiple emulsion, havebecome important in various industrial uses such as cosmetics, foodproducts, and medicines. Namely, while normal W/O type emulsions have aconfiguration in which a water phase is simply dispersed in an oilphase, the particle structure of multiple emulsions is such that, asshown in FIG. 1, an inner oil phase 14 is further dispersed in a waterphase 12 which has been dispersed in an outer oil phase 10. Accordingly,they are expected to yield special feel of use and effects which cannotbe obtained by simple O/W type and W/O type emulsions.

For example, since the inner oil phase 14 is blocked from the externalatmosphere by the water phase 12 and the outer oil phase 10, when anoil-soluble material which is easily oxidized is contained in the inneroil phase 14, its stability against oxidization is expected to beimproved as compared with the cases where it is contained in the oilphase of O/W type or W/O type emulsions.

Also, in recent years, silicone type bases such as dimethylpolysiloxanehave been widely used as a base for external preparations for skin orcosmetic preparations due to their favorable usabilities such as goodspreadability, refreshness, and lack of greasiness, as well as theirexcellent water resistance and oil resistance which make them resistantto being washed out by sweat and water. In particular, in suncarecosmetics, since they are universally used in summer, refreshing feel ofuse and those not easily washed out by sweat, sebum, or water arerequired, whereby such silicone bases are being used more frequently.

Of the oil-soluble agents usually added in cosmetic preparations andexternal preparations for skin, those hard to dissolve in silicone typeoils are not a few, however. For example, of the oil-soluble ultravioletabsorbers added in suncare cosmetic preparations, there are many whichhave a remarkably low solubility to silicone type bases. Accordingly, incosmetic preparations containing a large amount of a silicone type base,there has been a problem that, when such an ultraviolet absorber isadded therein, crystals of the ultraviolet absorber may deposit overtime.

In order to prevent crystals from depositing, it has been necessary torestrict the using amount of oil-soluble agents which are hard todissolve in silicone type oils or concurrently use a large amount ofoils such as polar oils to which the agents have a high solubility.Effect of the agent, however, usually depend on its amount added andcannot be sufficiently obtained when the using amount is restricted.Also, when non-silicone type oils such as polar oils are used in a largeamount, the amount of silicone type oils is restricted in emulsioncompositions, for example, due to problems in terms of formulation,whereby there are cases in which a large amount of silicone type oilscannot be added to make it difficult to yield satisfactory feel of useand resistance to both water and oil.

Further, since silicone type oils are totally different from the otherpolar and nonpolar oils in terms of structure and property, whennon-silicone type oils added in an oil phase of an emulsion such as W/Oor O/W together with a silicone type oil, it is difficult to select anemulsifier, emulsification conditions, and the like, thereby making itquite difficult, in general, to obtain an emulsion having a favorableemulsion stability.

These problems are considered to be solved by application of O/W/O typemultiple emulsion. Namely, in an O/W/O type multiple emulsion, since aninner oil phase 14 and an outer oil phase 10 are separated from eachother by a water phase 12, it is theoretically possible to make twokinds of oil contents such as a silicone type oil and a non-siliconetype oil which have different properties coexist independently from eachother in one emulsion system. For example, when an oil-soluble materialwhich is hard to dissolve in a silicone type oil and a non-silicone typeoil to which the material is soluble are added in one oil phase, whereasthe silicone type oil is added in the other oil phase, the material canbe prevented from depositing while these components are made to coexiststably in one emulsion system.

As a method of preparing a multiple emulsion, there has conventionallybeen known a so-called two-step emulsion technique in which an O/W typeemulsion formed by using a hydrophilic surfactant 16 is re-emulsified inan outer oil phase in which a lipophilic surfactant 18 has beendissolved. However, the emulsification stability of thus preparedmultiple emulsion may be so low that, over time, the inner oil phase 14and the outer oil phase 10 can merge with each other or the water phase12 can be incorporated therein, thereby finally dissociating the oils orwater. Since the emulsification stability of the multiple emulsionitself is quite low, the above-mentioned effects expected from the O/W/Otype multiple emulsion have not been fully attained.

In order to overcome these problems, various attempts have been made.For example, Japanese Examined Patent Publication No. 55-33294 disclosesa method in which a milk protein and cane sugar fatty acid ester areused together, while Japanese Examined Patent Publication No. 3-54709discloses a method in which polyglycerine fatty acid ester is compoundedin the outer oil phase. Also, Japanese Unexamined Patent Publication No.63-30405 discloses a method in which a specific kind of bentonite anddextrin fatty acid ester are respectively compounded in the water phaseand the outer oil phase.

However, even in the O/W/O type multiple emulsions prepared by theabove-mentioned conventional methods, the inner oil phase still tends tomerge with the outer oil phase, thereby reducing the remaining amount ofthe inner oil phase over time. Namely, since the inner oil phase 14 andthe outer oil phase 10 face each other with the water phase 12 andhydrophilic groups of the surfactants 16 and 18 therebetween, there isonly a very small barrier for preventing these oil phases 10 and 14 frommerging with each other. Also, since the inner oil phase 14 has to bepresent, it is difficult, physically or in techniques of manufacture,for the water phase 12 to have a small particle size. Accordingly, theO/W/O type multiple emulsion has a greater number of causes forunstableness as compared with the conventional O/W type or W/O typeemulsions. Therefore, the products prepared by the above-mentionedmethods have a shortcomings that the characteristics of the multipleemulsion are not sufficiently represented in their physical properties.

Also, while an O/W/O type multiple emulsion in which an ultravioletabsorber or an antioxidant is compounded in its inner oil phase hasrecently been reported in Japanese Unexamined Patent Publication No.7-101844, since the conventional technique is used for preparing such amultiple emulsion, its emulsification stability tends to be so low thatthe emulsion condition may be collapsed during a long period of storage,whereby the stability of the agent compounded in the inner oil phaseagainst oxidization over time can not be improved.

Thus, in the conventional multiple emulsions, those which are stableover time cannot be easily obtained. Also, for example, even when anoil-soluble agent is contained in the inner oil phase at the time ofpreparation, the inner oil phase may merge with the outer oil phase overtime, thereby reducing the remaining amount of the inner oil phase andfinally incorporating the inner oil phase into the outer oil phase.Accordingly, the agent and the oil in the inner oil phase may migrate tothe outer oil phase, whereby the effects expected from the O/W/O typeemulsion composition cannot be sufficiently obtained.

Also, in order to improve the stability of an emulsion, theabove-mentioned conventional methods include a step for rapidly coolingand plasticizing the emulsion subsequent to the heating step during itspreparation. In this case, the heating and rapid cooling stepsnecessitate a special apparatus and, accordingly, it is quite difficultfor thermally unstable ingredients such as vitamins to be compounded.

SUMMARY OF THE INVENTION

In view of the foregoing problems of the prior art, the object of thepresent invention is to provide a multiple emulsion having stabilitiesof the emulsified condition and the agent over time due to preventingits inner oil phase and outer oil phase from combining together.

As a result of diligent studies to achieve the above-mentioned object,the inventors have found that the inner oil phase and outer oil phaseare remarkably prevented from combining together when an organophilicclay mineral is present in the outer oil phase. It has also been foundthat, when an oil-soluble material is contained in the inner oil phasein such a multiple emulsion system, the material is prevented from beingoxidized and decomposed during a long period without migrating to theouter oil phase. Thus, the present invention has been accomplished.

Namely, the multiple emulsion in accordance with the present inventionis an O/W/O type multiple emulsion in which an O/W type emulsion isdispersed in a continuous outer oil phase, wherein said outer oil phasecontains an organophilic clay mineral.

Preferably, the organophilic clay mineral is obtained from awater-swellable clay mineral by treating with a quaternary ammonium typecationic surfactant and a nonionic surfactant.

Preferably, a blending ratio of the oil-in-water type emulsion to theouter oil phase is within a range of 2:3 to 19:1 by weight ratio.

Preferably, in the multiple emulsion in accordance with the presentinvention, the silicone type oil is contained in the oil phase.

Preferably, the silicone type oil is contained in the outer oil phase.

Preferably, the silicone type oil is within a range of 5 to 60 weight %with respect to a whole amount of the multiple emulsion.

Preferably, the silicone type oil has a boiling point which is 200° C.or less.

Preferably, in the multiple emulsion in accordance with the presentinvention, an inner oil phase contains an oil-soluble material.

Preferably, the oil-soluble material contained in the inner oil phase isslightly soluble in a silicone type oil and the silicone type oil isblended in the outer oil phase.

Also, the oil-soluble material included in the inner oil phase ispreferably one or more agent selected from the group consisting ofoil-soluble vitamins, oil-soluble ultraviolet absorbers, and unsaturatedfatty acids and the derivatives thereof which are easily oxidized.

Preferably, in the multiple emulsion in accordance with the presentinvention, a water phase contains a hydrophilic polymer.

Preferably, the hydrophilic polymer is one or more selected from thegroup of sodium alginate, carageenan, xanthan gum, gelatin, curdlan,agar, glucomannan, starch, hyaluronic acid, scleroglucan, schizophyllan,lentinan, pararomine, callose, raminarun, cellulose, methylcellulose,ethylcellulose, nitrocellulose, gum arabic, polyvinyl alcohol,carboxyvinyl polymer, carboxymethylcellulose, hydroxyethylcellulose,polyethylene glycol, tragacanth gum, garactan, guar gum, carob gum,karaya gum, pectin, guince seed, argecolloids, glycyrrhizinic acid,dextran, puluran, collagen, casein, albumen, carboxymethyl starch,methylhydroxypropyl starch, methylhydroxypropylcellulose, sodiumcellulose sulfate, hydroxypropylcellulose, propylene glycol alginate,polyvinylmethyl ether, polyvinyl pyrrolidone, polyoxyethylenepolyoxypropylene copolymer, sodium polyacrylate, polyethylacrylate,polyacryl amide, and polyethylene imine.

The method of preparing an oil-in-water-in-oil type multiple emulsion inaccordance with the present invention comprises the steps of:

preparing an oil in water-soluble solvent type emulsion by blendingcomponents of an inner oil phase into a mixture of a hydrophilicnonionic surfactant and a water-soluble solvent;

preparing an oil-in-water type emulsion by blending components of awater phase into said oil in water-soluble solvent type emulsion; and

preparing an oil-in-water-in-oil type multiple emulsion by dispersingand emulsifying said oil-in-water type emulsion in a mixture ofcomponents of an outer oil phase which contains an organophilic claymineral.

Preferably, in the method of the present invention, a silicone type oilis contained in the oil phase.

Preferably, in the method of the present invention, the silicone typeoil is contained in the outer oil phase.

Preferably, in the method of the present invention, the inner oil phasecontains an oil-soluble material.

Preferably, in the method of the present invention, the oil-solublematerial contained in the inner oil phase is slightly soluble in asilicone type oil and the silicone type oil is contained in the outeroil phase.

Preferably, in the method of the present invention, the oil-solublematerial included in the inner oil phase is one or more agent selectedfrom a group consisting of oil-soluble vitamins, oil-soluble ultravioletabsorbers, and unsaturated fatty acids and the derivatives thereof whichare easily oxidized.

Preferably, in the method of the present invention comprises the stepsof:

preparing an oil in water-soluble solvent type emulsion by blendingcomponents of an inner oil phase into a mixture of a hydrophilicnonionic surfactant and a water-soluble solvent;

preparing an oil-in-water type emulsion by blending components of awater phase which contains water and a hydrophilic polymer into said oilin water-soluble solvent type emulsion;

preparing an oil-in-water-in-oil type multiple emulsion by dispersingand emulsifying said oil-in-water type emulsion in a mixture ofcomponents of an outer oil phase which contains an organophilic claymineral; and

making the water phase gel by blending gelling agent of the hydrophilicpolymer into said oil-in-water-in-oil type multiple emulsion.

In the following, the configuration of the present invention will beexplained in detail.

When a hydrophilic surfactant is used to prepare an O/W type emulsionand then thus prepared emulsion and oil of an outer oil phase containingan organophilic clay mineral are mixed and emulsified together, theO/W/O type multiple emulsion (which may be simply referred to as"multiple emulsion" in the present application) of the present inventionis prepared.

As mentioned below, the organophilic clay mineral used in the presentinvention may be obtained when a water-swellable clay mineral is treatedwith a quaternary ammonium type cationic surfactant and a nonionicsurfactant.

The water-swellable clay mineral used here may be a kind of colloidalhydrous aluminum silicate generally expressed by the following formulaI:

    (X,Y).sub.A (Si,Al).sub.4 O.sub.10 (OH).sub.2 Z.sub.B.nH.sub.2 Oformula I

wherein

X=Al, Fe^(III), Mn^(III), or Cr^(III) ;

Y=Mg, Fe^(II), Ni, Zn, or Li;

Z=K, Na, or Ca;

A is 2 to 3; and B=1/3.

Specific examples thereof include natural or synthetic (where OH groupin the formula is substituted by fluorine) montmorillonite group such asmontmorillonite, saponite, and hectorite as well as synthetic mica knownunder such names as sodium silicic mica sodium or lithium taeniolite.The montmorillonite group includes commercially available products suchas Beegum, Kunipia, and Laponite, and the synthetic mica includescommercially available products such as Dimonite manufactured by TopyIndustries, Ltd.

Also, as the quaternary ammonium salt type cationic surfactant, thatexpressed by the following formula II may be used: ##STR1## wherein R₁is an alkyl group having 10 to 22 carbon atoms or benzyl group, R₂ ismethyl group or alkyl group having 10 to 22 carbon atoms, R₃ and R₄ arealkyl or hydroxyalkyl group having 1 to 3 carbon atoms, and X is halogenatom or methyl sulfate residue.

Examples thereof include dodecyltrimethylammonium chloride, myristyltrimethylammonium chloride, cetyltrimethyl ammonium chloride,stearyltrimethyl ammonium chloride, arachyltrimethyl chloride,behenyltrimethylammonium chloride, myristyldimethylethylammoniumchloride, cetyldimethylethylammonium chloride, chloride,arachyldimethylethylammonium chloride, behenyldimethylethylammoniumchloride, myristyldiethylmethylammonium chloride,cetyldiethylmethylammonium chloride, stearyldiethylmethylammoniumchloride, arachyldiethylmethylammonium chloride,behenyldiethylmethylammonium chloride, benzyldimethylmyristylammoniumchloride, benzyldimethylcetylammonium chloride,benzyldimethylstearylammonium chloride, benzyldimethylbehenylammoniumchloride, benzylmethylethylcetylammonium chloride,benzylmethylethylstearylammonium chloride, dibehenyldihydroxyethylammonium chloride, and their corresponding bromides as well asdipalmitylpropylethyl ammonium methyl sulfate.

In the present invention, at least one of the above-mentioned membersmay be arbitrarily selected.

Next, the nonionic surfactant used for treating the water-swellable claymineral together with the above-mentioned quaternary ammonium salt typecationic surfactant will be explained.

The nonionic surfactant used for the treatment of the clay mineral inthe present invention has an HLB value preferably within the range of 2to 16 and more preferably within the range of 3 to 12.

Here, the HLB value is calculated by the following Kawakami'sexpression:

    HLB=7+11.7×log (Mw/Mo)

wherein Mw is molecular weight of the part of the hydrophilic group andMo is molecular weight of the part of the lipophilic group.

Examples thereof include ethylene oxide addition type surfactantsincluding ether type surfactants such as oleyl ether added with 2 to 30moles of polyoxyethylene (referred to as POE(2-30) in the following),POE(2-35) stearyl ether, POE(2-20) lauryl ether, POE(1-20) alkyl phenylether, POE(6-18) behenyl ether, POE(5-25) 2-decylpentadecyl ether,POE(3-20) 2-decyltetradecyl ether, and POE(8-16) 2-octyldecyl ether;ester type surfactants such as POE(4-60) hardened castor oil, POE(3-14)fatty acid monoester, POE(6-30) fatty acid diester, and sorbitan fattyacid ester; and ether ester type surfactants such as POE(2-30) glycerylmonoisostearate, POE(10-60) glyceryl triisostearate, POE(7-50) castoroil monoisostearate, and POE(12-60) castor oil triisostearate. Also,examples of the nonionic surfactant include polyhydric alcohol fattyacid ester type surfactants including polyglycerine fatty acid esterssuch as decaglyceryl tetraoleate, hexaglyceryl triisostearate,tetraglyceryl diisostearate, diglyceryl diisostearate and glycerinefatty acid esters such as glyceryl monoisostearate and glycerylmonooleate, and include nonionic modified silicone surfactant such asdimethylpolysiloxane polyoxyalkylene copolymer shown by the followingformula III; ##STR2## wherein a is an integer from 1 to 5, b is aninteger from 7 to 15, c is an integer from 0 to 4, m is an integer from20 to 100, n is an integer from 1 to 5, and R is hydrogen or an alkylgroup having 1 to 5 carbon atoms.

Among these ingredients, in particular, the follows are preferably used;polyglycerine fatty acid esters not lower than triglycerine such asdecaglyceryl tetraoleate, hexaglyceryl triisostearate, and tetraglyceryldiisostearate; ethylene oxide addition type nonionic surfactantsincluding POE-added ether type surfactants such as POE(2-12) oleylether, POE(3-12) stearyl ether, POE(2-10) lauryl ether, POE(2-10)nonylphenyl ether, POE(6-15) behenyl ether, POE(5-20) 2-decylpentadecylether, POE(5-17) 2-decyltetradecyl ether, and POE(8-16) 2-octyldecylether; POE-added ester type surfactants such as POE(10-20) hardenedcastor oil, POE(5-14) monooleate, POE(6-20) dioleate, POE(5-10) sorbitanoleate; and POE-added ether ester type surfactants such as POE(3-15)glyceryl monoisostearate and POE(10-40) glyceryl triisostearate; andnonionic modified silicone surfactant such as dimethylpolysiloxanepolyoxyalkylene copolymer shown by formula III mentioned above.

In the present invention, at least one of these nonionic surfactants maybe arbitrarily selected for use.

The organophilic clay mineral used in the present invention can beobtained when a water-swellable clay mineral, a quaternary ammonium salttype cationic surfactant, and a nonionic surfactant are dispersed andstirred in a low-boiling solvent such as water, acetone, or loweralcohol and then the low-boiling solvent is removed. Alternatively, itmay be obtained when, after the water-swellable clay mineral and thequaternary ammonium salt type cationic surfactant are treated in alow-boiling solvent so as to yield a cationic denatured clay mineral,the latter is treated with the nonionic surfactant and then thelow-boiling solvent is removed.

In the following, thus prepared organophilic clay mineral will beexplained. Among clay minerals, Na-type montmorillonite, for example,which belongs to smectites and is water-swellable, becomes a hydrophobicorganophilic montmorillonite upon cation exchange reaction with aquaternary ammonium salt type organic cation. Further, it encloses thenonionic surfactant so as to form an inclusion compound which may bereferred to as "complex", and then swells in an oil to form a viscousoily gel. It is considered that the nonionic surfactant is enclosed in apolar site between montmorillonite layers (which may be referred to as"silicate layers") which does not participate in the cation exchangereaction and that the oil further infiltrates between these layers suchthat the layers swell and form an oily gel (Journal of the Japan OilChemists' Society, vol. 40, no. 6, pp. 491-496, 1991).

Thus obtained organophilic clay mineral has such a structure that thedistance between the layers of the water-swellable clay mineral isbroadened due to the quaternary ammonium type cationic surfactant andnonionic surfactant infiltrating therein. Accordingly, when the longsurface distance is measured by X-ray diffraction, it can be confirmedwhether the quaternary ammonium type cationic surfactant and thenonionic surfactant are chemically and physically adsorbed or not.

Also, when thus obtained organophilic clay mineral is subjected toSoxhlet extraction by using chloroform, ether, or the like, thesurfactant physically adsorbed between the layers is washed out.Accordingly, when this extract is subjected to gas chromatographyanalysis, measurement of the thermal decomposition temperature, ormeasurement of the thermal decomposition amount (DTA-TG measurement),the amount of the surfactant physically adsorbed can be confirmed. Here,since the amount of the quaternary ammonium salt type cationicsurfactant which is chemically bonded in organophilic clay mineral dueto cationic exchange cannot be extracted by Soxhlet extraction, thewhole amount of the quaternary ammonium salt type cationic surfactantwhich chemically bonded and physically adsorbed in the organophilic claymineral can be determined when the organophilic clay mineral issubjected to DTA-TG measurement.

While not restricted in particular, the amount of the quaternaryammonium salt type cationic surfactant used in the organophilic claymineral is preferably 60 to 140 milliequivalents (referred to as "meq"in the following) with respect to 100 g of the water-swellable claymineral. Also, the amount of the nonionic surfactant in the organophilicclay mineral is preferably 5 to 100 g and more preferably 15 to 50 gwith respect to 100 g of the water-swellable clay mineral.

Such an organophilic clay mineral is disclosed, for example, in JapaneseExamined Patent Publication No. 2-32015 and has been known to beeffective in preparing a stable W/O emulsion. However, it has not at allbeen known to be effective in stabilizing multiple emulsions and, inparticular, in preventing their inner oil phase and outer oil phase fromcombining together.

In an O/W/O type multiple emulsion, when such an organophilic claymineral is contained in its outer oil phase, its inner oil phase andouter oil phase are prevented from combining together, thereby yieldingan O/W/O type multiple emulsion having a very high stability over time.Further, when an oil-soluble agent is compounded in the inner oil phaseof such a system, the oil-soluble agent is prevented from beingoxidized, whereby an excellent stability of the agent can be obtained.

The amount of the organophilic clay mineral used in the multipleemulsion composition is preferably 0.1 to 5% by weight and morepreferably 0.5 to 3% by weight. Below 0.1%, the effects of the additionof the organophilic clay mineral may not be exhibited, whereby a stablemultiple emulsion may not be obtained. Specifically, the inner oil phasemay disappear over time and thereby the multiple emulsion can not bemaintained. Above 5%, on the other hand, practical problems may occur.For example, the prepared emulsion may have high viscosity, lowspreadability, roughness, or no transparency.

In the present invention, as the organophilic clay mineral obtained asmentioned above is compounded in the outer oil phase, a wide range ofoils from polar oils to nonpolar oils can be used as an oil phasecomponent. Examples of the oils include hydrocarbon oils such as liquidparaffin, squalane, isoparaffin, and branched-chain light paraffin;ester oils such as isopropyl myristate, cetyl isooctanoate, and glyceryltrioctanoate; and silicone type oils.

When a silicone type oil is used, an emulsion having favorable oilresistance, water resistance, and feel of use can be obtained. In thepresent invention, though a variety of silicone oils can be widely usedas a silicone type oil, those having a boiling point of 200° C. or lessat normal pressure are preferable from the viewpoint of feel of use andformulation. Examples thereof include a chain polysiloxane such asdimetyhlpolysiloxane, methylphenylpolysiloxane, andmethylhydrogenpolysiloxane as well as a cyclopolysiloxane such asdecamethylcyclopentasiloxane, dodecamethyl cyclohexasiloxane, andtetramethyltetrahydrogencyclotetrasiloxane. Among them, when a-volatilesilicone type oil such as volatile chain polysiloxane or volatile cyclicpolysiloxane is used, oily feel is harder to remain when applied to theskin as compared with a normal silicone type oil, whereby it ispreferably used when refreshing feel of use is required. Examples ofvolatile chain polysiloxane include dimethylpolysiloxane having lowdegree of polymerization (degree of polymerization: 3 to 7), andexamples of volatile cyclic polysiloxane includedecamethylcyclopentasiloxane and octamethylcyclotetrasiloxane.

In the multiple emulsion of the present invention, though the amount ofsilicone type oil added therein can be appropriately selected, it ispreferably 5% to 60% by weight, particularly preferably 5% to 40% byweight, and further preferably 15% to 40% by weight with respect to thewhole multiple emulsion amount. When the amount of silicone type oiladded is too less, water resistance, oil resistance, feel of use, andthe like may not be obtained sufficiently; whereas, when it is too much,there are cases where it becomes difficult to stabilize the emulsion.

In the present invention, though these silicone type oils can also beadded in the inner oil phase, they are preferably added in the outer oilphase. When a silicone type oil is added in the outer oil phase, whilethe amount of the silicone type oil added with respect to the wholeamount of the outer oil phase can be selected within the range of 8% to100% by weight depending on the ratio of the outer oil phase to themultiple emulsion, it is preferably 60% by weight or more andparticularly preferably 90% by weight or more.

According to one of the most preferable embodiments in the O/W/O typemultiple emulsion containing a silicone type oil in accordance with thepresent invention, the inner oil phase is a non-silicone type oil,whereas the outer oil phase is a silicone type oil. Also, according toone of preferable embodiments, the inner oil phase is a non-siliconetype oil, whereas the outer oil phase is a mixture of a silicone typeoil and a non-silicone type oil.

The hydrophilic polymer in the present invention raises viscosity of thewater phase, thereby suppressing coalescence of the inner oil phase andits migration to the outer oil phase. Also, upon use, when thehydrophilic polymer in the water phase is made to gel, the agentdissolved in the inner oil phase can be gradually released. Namely,since the gradually releasing characteristics depends on viscosity ofthe water phase and the hardness of the gel, the releasing speed can befreely adjusted when the kind of the polymer and the concentrationthereof are controlled. For examples of the hydrophilic polymer used,sodium alginate, carageenan, zansan gum, gelatin, cardrant, agar,glucomannan, starch, hyaluronic acid, scleroglucan, syzofiran, renchnum,paramylon, kallose, laminaran, cellulose, methylcellulose,ethylcellulose, nitrocellulose, gum arabic, polyvinyl alcohol,carboxyvinyl polymer, carboxymethylcellulose, hydroxyethylcellulose,polyethylene glycol, tragacanth gum, garactan, guar gum, carob gum,karaya gum, pectin, guince seed, argecolloids, glycyrrhizinic acid,dextran, puluran, collagen, casein, albumen, carboxymethyl starch,methylhydroxypropyl starch, methylhydroxypropylcellulose, sodiumcellulose sulfate, hydroxypropylcellulose, propylene glycol alginate,polyvinylmethyl ether, polyvinyl pyrrolidone, polyoxyethylenepolyoxypropylene copolymer, sodium polyacrylate, polyethylacrylate,polyacryl amide, and polyethlene imine can be cited. In the presentinvention, one or more can be selected from them.

The method of preparing the O/W type emulsion using the hydrophilicsurfactant is not restricted in particular as long as a stable emulsioncan be obtained thereby. An example of such a method comprises a firststep of adding a hydrophilic nonionic surfactant to a water-solublesolvent and then adding components of an inner oil phase thereto so asto form an oil in water-soluble solvent type emulsion and a second stepof adding components of a water phase to this emulsion (e.g., JapaneseExamined Patent Publication No. 57-29213). When such an emulsifyingtechnique is used for preparing the O/W type emulsion, the inner oilphase can be compounded minutely and stably. Accordingly, it isparticularly preferable for preparing the multiple emulsion inaccordance with the present invention.

The water-soluble solvent used in this emulsifying technique dissolvesthe hydrophilic nonionic surfactant and efficiently makes the surfactantadsorb on the interface with respect to the oil phase which issubsequently added thereto. It can be selected from a very wide range ofagents such as lower monohydric alcohols, lower polyhydric alcohols,ketones, aldehydes, ethers, amines, lower fatty acids, and others aslong as they are hydrophilic and can dissolve the nonionic surfactant.Specific examples thereof include the water-soluble solvents disclosedin Japanese Examined Patent Publication No. 57-29213.

As the hydrophilic nonionic surfactant, ethylene oxide and/or propyleneoxide addition products are preferable. Specific examples thereofinclude the hydrophilic nonionic surfactants disclosed in JapaneseExamined Patent Publication No. 57-29213.

Further, when thus obtained O/W type emulsion is mixed and emulsified inthe outer oil phase containing the above-mentioned organophilic claymineral while being stirred, the aimed O/W/O type multiple emulsion canbe obtained. While the emulsifier used at this time is not restricted inparticular, disper (TK HOMO DISPER; Tokushu Kika Kogyo Co., Ltd) or thelike is preferably used.

Here, the ratio of the O/W type emulsion to the outer oil phasecontaining the organophilic clay mineral is preferably 2:3 to 19:1 andmore preferably 1:1 to 4:1. When the O/W type emulsion has a mixingratio lower than 2:3, the prepared multiple emulsion may have lowviscosity and the emulsification stability may deteriorate over time. Onthe other hand, when the O/W type emulsion has a mixing ratio greaterthan 19:1, the phase inversion may occur during emulsification withstirring, thereby failing to form a multiple emulsion.

In the multiple emulsion formed in the foregoing manner, as shown inFIG. 2, an organophilic clay mineral 20 is adsorbed on the interfacebetween a water phase 12 and an outer oil phase 10, whereby an inner oilphase 14 and the outer oil phase 10 are separated from each other by theorganophilic clay mineral 20 structurally and physically. As a result,the inner oil phase 14 can be effectively prevented from combining withthe outer oil phase 10, thereby attaining an excellent emulsificationstability. The effect obtained in the present invention that stabilityof the agent contained in the inner oil phase to oxidation is improvedis considered to be due to the fact that it is hardly possible for theagent to come into direct contact with the outer oil phase or externalatmosphere since the oil-soluble agent blended in the inner oil phase atthe time of its preparation cannot move to the outer oil phase accordingto the mechanism explained above. Also, since heating during thepreparation step is not required in particular, thermal decompositionduring the preparation hardly occurs, whereby it is fully possible foringredients having a low thermal stability to be added.

Further, for example, when an oil-soluble agent which is hard todissolve in a silicone type oil content and a polar oil to which theagent has a high solubility are added in the inner oil phase, whereasthe silicone type oil is added in the outer oil phase, crystals of theagent can be prevented from depositing while these ingredients canstably coexist in one emulsion system. Also, its feel of use has afavorable spreadability and no greasiness, thereby making it quitesuperior to simple W/O type emulsions containing a silicone type oil.

The oil-soluble agent used in the present invention can be selectedaccording to the aimed purpose. While it is not restricted in particularas long as it is generally used in cosmetics and medicines, examplesthereof include oil-soluble vitamins, oil-soluble ultraviolet absorbers,and unsaturated fatty acids and the derivatives thereof. In particular,easily oxidizable oil-soluble materials are effectively used since theiroxidation stability can be improved.

Examples of the oil-soluble vitamins include, as vitamin A group,retinol, 3-dehydroretinol, retinal, 3-dehydroretinal, retinoic acid,3-dehydroretinoic acid, and esters such as vitamin A acetate and vitaminA palmitate and, as provitamin A, carotenoids and xanthophylls such asα-, β-, and γ-carotenes, β-cryptoxanthin, and echinenone. Examples ofvitamin D include vitamin D₂ to D₇. Examples of vitamins E include α-,β-, γ-, and δ-tocopherols, α-, β-, γ-, and δ-tocotrienols and esterssuch as vitamin E acetate and vitamin E nicotinate. Examples of vitaminK include vitamin K₁ to K₃.

Examples of ultraviolet absorbers include benzophenone type ultravioletabsorbers such as 2,4-dihydroxybenzophenone,2,2'-dihydroxy-4-methoxybenzo phenone,2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-4'-methylbenzophenone and others such as 3-(4'-methylbenzylidene)-d,l-camphor,3-benzylidene-d,l-camphor, 4-methoxy-4'-t-butylbenzoylmethane. Thosewhich are solid at normal temperature may be dissolved in the oilcomponent and then added.

Examples of unsaturated fatty acids include oleic acid, linoleic acid,α-linolenic acid, γ-linolenic acid, dihomo-γ-linolenic acid, arachidonicacid, eicosapentaenic acid, and docosahexaenic acid. Examples ofderivatives thereof include alchol esters such as methyl ester, ethylester, and propyl ester; glycerides such as monoglyceride, diglyceride,and triglyceride; phospholipids such as phosphatidylcoline,phosphatidylethanolamine, and sphingomyelin; glycolipids such asglucosylceramide; ceramides; waxs; and esters of cholesterol. In thepresent invention, when an unsaturated fatty acid having high degree ofunsaturation such as that having three or more unsaturated bonds in amolecule is selected from them, its very high stability can be obtainedas well.

An oil-soluble agent which is hard to dissolve in a silicone type oil isalso preferable as an oil-soluble material in the present inventionsince it can be prevented from depositing crystals when added in an oilphase different from that containing a silicone type oil as mentionedabove. Also, when the agent is a liquid, it can be prevented fromseparation. Examples of such slightly soluble agents to silicone typeoils include, in addition to the above-mentioned ultraviolet absorbers,Antalon (polyvinylpyrrolidone alkyl copolymer), which is used as a filmformer in sunscreen preparations, and liquid perfumes such as hexenol,3-octanol, 1-octene-3-ol, 9-deserol, linalool, and geraniol, which arerelatively high polar and have low solubility to silicone type oils.

Since the multiple emulsion in accordance with the present invention hasexcellent stabilities of emulsification and the agent, application invarious fields can be expected. In particular, it is usable in cosmeticand medical external preparations for skin such as a milky lotion, acream, and a foundation. Also, cosmetics for heir such as a shampoo anda rinse can be included.

The multiple emulsion of the present invention can additionally compriseother components which is commonly used in cosmetics and medicalexternal preparations for skin when they will not detract the effects ofthe present invention. Examples thereof include alcohols, humectants,whitening agents, ultraviolet absorbers, preservatives, cheletingagents, perfumes, coloring agents, pigments, dyes, surfactants, and theother agents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual view showing the conventional O/W/O multipleemulsion and

FIG. 2 is a conceptual view showing the O/W/O multiple emulsion inaccordance with the present invention.

EXAMPLES

In the following, the present invention will be explained in furtherdetail with reference to specific examples thereof. Here, the presentinvention is not restricted to these examples. The blending ratio in thefollowing is indicated by % by weight unless otherwise specified.

Preparation of Organophilic Clay Mineral

First, a method of preparing the organophilic clay mineral used in thepresent invention and a method for confirming it will be explained indetail.

Preparation 1

At 50° C., 45 g of benzyldimethylstearylammonium chloride (correspondingto about 100 meq) and 30 g of POE(6) lauryl ether were dissolved to form500 ml of an aqueous solution. Then, to this solution, 100 g of Beegum(product name of Vanderbilt Co., USA), namely, a water-swellable claymineral, were added. The resulting mixture was sufficiently dispersedand mixed for about 30 minutes by a disper. After water was removed by afilter, the residue was dried for about one day and night so as to yieldthe aimed organophilic clay mineral. In order to judge whetherbenzyldimethylstearyl ammonium chloride (referred to as "(A)") andPOE(6) lauryl ether (referred to as "(B)") had been chemically andphysically adsorbed or not, X-ray diffraction was performed as well asthe thermal decomposition amount of the surfactant was measured byDTA-TG technique and compared with the water-swellable clay mineral(Beegum).

Table 1 shows the results thereof.

                  TABLE 1                                                         ______________________________________                                                                     Organophilic clay                                                Clay mineral before                                                                        mineral of                                       Measurement item                                                                              treatment (Beegum)                                                                         Preparation 1                                    ______________________________________                                        Distance between layers                                                                       13.2 Å   40.1 Å                                       by X-ray diffraction                                                          Thermal decomposition amount*                                                                 0            (A)      (B)                                     of the surfactants by DTA-TG 101 meq  29 g                                    ______________________________________                                         *Expressed as an amount per 100 g of the waterswellable clay mineral.    

As evidenced by Table 1, the distance between layers of the organophilicclay mineral of Preparation 1 is remarkably wider than that of thewater-swellable clay mineral before treatment. As can be seen from theresults of DTA-TG measurement, it is caused by binding ofbenzyldimethylstearylammonium chloride (A) and POE(6) lauryl ether (B)to the water-swellable clay mineral.

Preparation 2

In 50 ml of ethanol in which 20 g of POE(15) 2-octyldecyl ether(referred to as "(C)") had been dissolved, 100 g of Benton-38, namely,an organophilic clay mineral, were sufficiently dispersed and mixed by alaboratory homogenizer. Benton-38, a product name of National Red Co.,USA, is an organophilic clay mineral formed when 100 g ofmontmorillonite, namely, a water-swellable clay mineral, were treatedwith 100 meq of distearyldimethylammonium chloride (referred to as"(D)").

After ethanol was removed by an evaporator, the residue was dried forabout one day and night so as to yield the aimed organophilic claymineral. As in the case of Preparation 1, the X-ray diffraction and thethermal decomposition amount of the surfactant by DTA-TG technique wereused to judge whether there had been modification or not. Here, Soxhletextract of the organophilic clay mineral by chloroform was subjected toDTA-TG measurement as a sample.

Table 2 shows the results thereof.

                  TABLE 2                                                         ______________________________________                                                                    Organophilic clay                                                             mineral of                                        Measurement item                                                                              Benton-38   Preparation 2                                     ______________________________________                                        Distance between layers                                                                       26.8 Å  36.8 Å                                        by X-ray diffraction                                                          Thermal decomposition amount*                                                                 (D)      (C)    (D)    (C)                                    of the surfactants                                                                            12 meq   0      12 meq 20 g                                   in Soxhlet extract by DTA-TG                                                  ______________________________________                                         *This is the same as Table 1.                                            

As evidenced by Table 2, even when an organophilic clay mineral(Benton-38) which has been treated with quaternary ammonium typecationic surfactant is used, the distance between its layers is furtherwidened when treated with the nonionic surfactant (C). As in the case ofPreparation 1, it is considered to be caused by the adsorption of thenonionic surfactant. Here, the amount of the quaternary ammonium salttype cationic surfactant extracted by Soxhlet extraction corresponds tothat physically adsorbed in the organophilic clay mineral (Benton-38)which has been organically denatured by cationic exchange reaction,while that chemically bonded in Benton-38 due to cationic exchangecannot be extracted by Soxhlet extraction. As shown in Preparation 1,the whole amount of the quanternary ammonium salt type cationicsurfactant which chemically bonded and physically adsorbed in theorganophilic clay mineral can be determined by DTA-TG techniquemeasurement of the organophilic clay mineral.

Method of Evaluating Emulsification Stability of Multiple Emulsion

In the examples which will be explained later, the emulsificationstability of the multiple emulsion was evaluated as follows:

1) Observation of the Emulsified State

After the emulsion prepared had been kept at room temperature (RT) forsix months or at 50° C. in an incubator for one month, its emulsifiedstate was observed by an optical microscope and naked eyes. The casewhere no abnormality was observed (where emulsion conditions andparticles are uniform) was evaluated as good (⊚), the case where noabnormality was observed by naked eyes though slight fluctuation of theparticle size was observed by the microscope was evaluated as fair (O),and the case where abnormality was observed (where water or an oil wasseparated, particles become large, etc) was evaluated as poor (X).

2) Inner Oil Phase Remaining Ratio

This is an experiment for showing that the inner oil phase is notabsorbed by the outer oil phase.

i) Qualitative Experiment

An O/W/O type multiple emulsion was prepared and then the change of itsstate over time was observed by a microscope. In unstable systems, theinner oil phase disappears and the emulsion becomes a simple W/O typeemulsion finally. In order to perform an accelerated test, thisexperiment was effected at a high temperature of 50° C.

ii) Quantitative Experiment

An oil-soluble marker agent (phthalic acid diester) was dissolved in theinner oil phase so as to prepare an O/W/O type multiple emulsion. Then,this emulsion was centrifuged so as to forcibly separate the oils of theouter oil phase. The marker concentration in the outer oil phase wasquantitatively determined and then subtracted from the wholeconcentration to calculate the marker concentration in the inner oilphase. As this process was performed over time, the state of movement ofthe inner oil phase into the outer oil phase could be observed, therebycalculating the inner oil phase remaining ratio.

Method of Evaluating Agent Stability

1) Agent Remaining Ratio

After sample emulsions were kept at 50° C. in an incubator for onemonth, the agent concentration in each sample was quantitativelydetermined by HPLC technique and the remaining ratio (%) of each agentwith respect to its charged amount was calculated. According to theremaining ratio, the agent stability was indicated as follows:

⊚: remaining ratio is not lower than 90% with respect to charged amount.

O: remaining ratio is at least 80% but less than 90% with respect tocharged amount.

Δ: remaining ratio is at least 60% but less than 80% with respect tocharged amount.

X: remaining ratio is less than 60% with respect to charged amount.

2) Crystal Deposit

The samples were stored at 50° C. for a month and then observed whetherthe agent deposited by light microscope.

O: no crystal deposit is observed(none).

Δ: crystal deposit is slightly observed(slight).

X: crystal deposit is remarkably observed(deposit).

Method of Evaluating Feel of Use

Each of samples prepared was applied on skin of 10 special panels,whereby the feeling test was performed. The result of evaluation wasindicated as follows:

⊚: 8 or more panels answered that it was free of greasiness.

O: 6 or 7 panels answered that it was free of greasiness.

Δ: 4 or 5 panels answered that it was free of greasiness.

X: 3 or less panels answered that it was free of greasiness.

EXAMPLE 1

First, the inventors prepared O/W, W/O, and O/W/O type emulsions byconventional techniques with some surfactants according to theprescription shown in Table 3 to Table 5 and evaluated theemulsification stability of the emulsions.

                  TABLE 3                                                         ______________________________________                                        O/W Type Emulsion                                                                                      Example                                              Constituent              1-1                                                  ______________________________________                                        (a) Surfactant phase                                                          1,3-Butanediol           21                                                   Purified water            2                                                   POE(60) hardened castor oil                                                                             2                                                   (b) Oil phase                                                                 Liquid paraffin          33                                                   (c) Water phase                                                               Purified water           42                                                   Emulsification stability (observation of the state)                           RT                       ◯                                        50° C.            ◯                                        ______________________________________                                    

<Method of Preparation>

Into a mixture prepared by uniformly dissolved ingredient (a) listed inTable 3, ingredient (b) was mixed and emulsified while being stirred.Then, ingredient (c) was added thereto and mixed therewith to yield anO/W type emulsion.

                  TABLE 4                                                         ______________________________________                                        W/O Type Emulsion                                                                          Example                                                          Constituent    1-2    1-3    1-4  1-5  1-6  1-7                               ______________________________________                                        (a) Surfactant                                                                POE(3) oleyl ether                                                                            1     --     --   --   --   --                                POE(2) oleyl ether                                                                           --      5     --   --   --   --                                Sorbitan monostearate                                                                        --     --      1   --   --   --                                Sorbitan monostearate                                                                        --     --     --    5   --   --                                POE(10) hardened castor oil                                                                  --     --     --   --   10   --                                POE(10) hardened castor oil                                                                  --     --     --   --   --    5                                (b) Oil phase                                                                 Liquid paraffin                                                                              39     35     39   35   30   35                                (c) Water phase                                                               Ion-exchanged water                                                                          60     60     60   60   60   60                                Emulsification stability                                                      (observation of the state)                                                    RT             ◯                                                                        ◯                                                                        ◯                                                                      ◯                                                                      ◯                                                                      ◯                     50° C.  ◯                                                                        ◯                                                                        ◯                                                                      ◯                                                                      ◯                                                                      ◯                     ______________________________________                                    

<Method of Preparation>

In Table 4, the above-mentioned ingredients (a) and (b) were mixed andthen ingredient (c) was mixed and emulsified therein while being stirredso as to yield the aimed W/O type emulsion.

                  TABLE 5                                                         ______________________________________                                        O/W/O Type Emulsion                                                                        Example                                                          Constituent    1-8    1-9    1-10 1-11 1-12 1-13                              ______________________________________                                        (a) O/W phase                                                                 O/W type emulsion                                                                            70     70     70   70   70   70                                of Example 1-1                                                                (b) Outer oil phase                                                           Liquid paraffin                                                                              29     25     29   25   20   25                                (c) Lipophilic surfactant                                                     POE(3) oleyl ether                                                                            1     --     --   --   --   --                                POE(2) oleyl ether                                                                           --      5     --   --   --   --                                Sorbitan monostearate                                                                        --     --      1   --   --   --                                Sorbitan monostearate                                                                        --     --     --    5   --   --                                POE(10) hardened castor oil                                                                  --     --     --   --   10   --                                POE(10) hardened castor oil                                                                  --     --     --   --   --    5                                Emulsification stability                                                      Observation of the state                                                      RT             X      X      X    X    X    X                                 50° C.  X      X      X    X    X    X                                 Inner oil phase remaining                                                                    <5     <5     <5   <5   <5   <5                                ratio (after 8 weeks at 50° C.)                                        ______________________________________                                    

<Method of Preparation>

In Table 5, ingredients (b) and (c) were mixed and then the O/W typeemulsion (a) of Example 1-1 was mixed and emulsified in the ingredient(b)+(c) while being stirred so as to yield the aimed O/W/O type multipleemulsion.

According to Tables 3 and 4, a considerably high emulsificationstability can be attained in O/W type emulsions and W/O type emulsionsby selecting appropriate surfactants. However, when a stable O/Wemulsion was dispersed in an outer oil phase to form an O/W/O typeemulsion, the emulsification stability of thus obtained O/W/O emulsionwas greatly deteriorated, whereby the inner oil phase exuded into theouter oil phase.

Therefore, the inventors studied the effect of an organophilic claymineral on multiple emulsion stabilization and, in particular, theeffect on prevention of its inner oil phase and outer oil phase fromcombining together as follows.

                  TABLE 6                                                         ______________________________________                                                        Example                                                       Constituent       1-14   1-15   1-16 1-17 1-18                                ______________________________________                                        (a) O/W phase                                                                 O/W type emulsion 70     70     70   70   70                                  of Example 1-1                                                                (b) Outer oil phase                                                           Liquid paraffin   28     28     28   28   28                                  (c) Surfactant in outer oil phase                                             Organophilic clay mineral                                                                        2     --     --   --   --                                  (Preparation 1)                                                               Unmodified clay mineral(Beegum)                                                                 --      2     --   --   --                                  Benzyldimethylstearyl                                                                           --     --      2   --   --                                  ammonium chloride                                                             POE(6) lauryl ether                                                                             --     --     --    2   --                                  Benzyldimethylstearylammonium                                                                   --     --     --   --    2                                  chloride +                                                                    POE(6) lauryl ether                                                           Emulsification stability                                                      Observation of the state                                                      RT                ◯                                                                        X      X    X    X                                   50° C.     ◯                                                                        X      X    X    X                                   Inner oil phase remaining ratio                                                                 98     <5     <5   <5   <5                                  (after 8 weeks at 50° C.)                                              ______________________________________                                    

<Method of Preparation>

In a manner similar to the method of Table 5 shown above, the O/W/O typemultiple emulsion was prepared by the prescription shown in Table 6.

As can be seen from Table 6, when the organophilic clay mineral wascompounded in the outer oil phase, an emulsion which was quite good inboth stability of the emulsification state and inner oil phase remainingratio was obtained.

On the other hand, when the unmodified clay mineral,benzyldimethylstearyl ammonium chloride, and POE (6) lauryl ether, whichwere constituents of the organophilic clay mineral, were used separatelyor in combination, the high emulsification stability such as thoseobtained when the organophilic clay was compounded could not obtained.

Accordingly, it is understood that the effect of the organophilic claymineral on the stability of the multiple emulsion is specific and thatthe emulsification stability of the multiple emulsion cannot be improvedwhen the stable O/W type emulsion is simply substituted for a waterphase of the stable W/O type emulsion.

EXAMPLE 2

Next, a preferable composition of the multiple emulsion of the presentinvention was studied.

(1) Composition

                  TABLE 7                                                         ______________________________________                                        Composition of O/W Type Emulsion                                              Constituent         Content                                                   ______________________________________                                        (a) Surfactant phase                                                          1,3-Butanediol      21                                                        Purified water       2                                                        POE(60) hardened castor oil                                                                        2                                                        (b) Inner oil phase                                                           Liquid paraffin     33                                                        (c) Water phase                                                               Purified water      42                                                        ______________________________________                                    

                  TABLE 8                                                         ______________________________________                                        Composition of Outer oil phase                                                Constituent         Content                                                   ______________________________________                                        (d) Surfactant                                                                Organophilic clay mineral                                                                          7                                                        of Preparation 1                                                              (e) Outer phase oil                                                           Liquid paraffin     93                                                        ______________________________________                                    

                  TABLE 9                                                         ______________________________________                                        Constitutional Ratio of O/W/O Type Multiple Emulsion                                     Amount of O/W                                                                 type emulsion                                                                             Amount of outer oil phase                              Example    (parts by weight)                                                                         (parts by weight)                                      ______________________________________                                        Example 2-1                                                                              50          50                                                     Example 2-2                                                                              60          40                                                     Example 2-3                                                                              70          30                                                     Example 2-4                                                                              80          20                                                     Example 2-5                                                                              35          65                                                     Example 2-6                                                                              97           3                                                     ______________________________________                                    

(2) Method of preparation

First, into the mixture of uniformly dissolved ingredient (a) shown inTable 7, ingredient (b) was mixed and emulsified while being stirred.Then, ingredient (c) was added thereto and mixed therewith to yield anO/W type emulsion.

Thereafter, the outer oil phase component shown in Table 8 was mixed. Inthis outer oil phase, the O/W type emulsion prepared above was mixed andemulsified while being stirred to yield the aimed O/W/O type multipleemulsion. Here, the ratio of the O/W type emulsion to the outer oilphase was changed as shown in Table 9 to form Examples 2-1 to 2-6.

(3) Result

                  TABLE 10                                                        ______________________________________                                        Evaluation of Emulsion Characteristics                                                Emulsion form                                                                          Emulsification                                                                           Inner oil phase                                           directly after                                                                         stability  remaining ratio*                                  Outer oil phase                                                                         preparation                                                                              RT     50° C.                                                                       (50° C., 1 month)                    ______________________________________                                        Ex. 2-1   O/W/O      ◯                                                                        ◯                                                                       93.0%                                       Ex. 2-2   O/W/O      ⊚                                                                     ◯                                                                       95.5                                        Ex. 2-3   O/W/O      ⊚                                                                     ⊚                                                                    98.6                                        Ex. 2-4   O/W/O      ⊚                                                                     ◯                                                                       92.8                                        Ex. 2-5   O/W/O      X      X     --                                          Ex. 2-6   O/W/O + O/W                                                                              X      X     --                                          ______________________________________                                    

As can be seen from Table 10, since the amount of the outer oil phasewas greater than the ratio expressed by the O/W type emulsion to theouter oil phase ratio of 2:3, while an O/W/O type emulsion was formeddirectly after the emulsification, Example 2-5 exhibited an inferioremulsification stability as compared with Examples 2-1 to 2-4, wherebyfloating of oil was recognized in both of room temperature storage and50° C. storage. Also, as shown in Example 2-6, when the O/W typeemulsion was greater than the ratio expressed by the O/W type emulsionto the outer oil phase ratio of 19:1, phase inversion occurred duringemulsification and dispersion, whereby it was confirmed that the O/W/Oand O/W types coexisted in the emulsion prepared.

Accordingly, the ratio of O/W type emulsion to the outer oil phase iswithin the range of 2:3 to 19:1, preferably.

COMPARATIVE EXAMPLE 1

Outer oil phases were prepared according to compositions of ComparativeExamples 1-1 to 1-6 shown in the following Table 11. In each outer oilphase, the lipophilic surfactant commonly used for preparing theconventional W/O type emulsion was used therein.

Further, an O/W type emulsion prepared in a manner similar to Table 7 ofExample 2 and each of the outer oil phases of Comparative Examples shownin Table 11 were mixed and emulsified together at a ratio of 7:3 byweight.

The emulsification stability of thus prepared emulsion was evaluated ina manner similar to Example 2.

                  TABLE 11                                                        ______________________________________                                        Composition of Outer Oil Phase                                                         Lipophilic surfactant                                                                            Oil                                               Outer oil phase                                                                        (parts by weight)  (parts by weight)                                 ______________________________________                                        Comp. Ex. 1-1                                                                          POE(3)oleyl ether (1)                                                                            liquid paraffin (99)                              Comp. Ex. 1-2                                                                          POE(3)oleyl ether (5)                                                                            liquid paraffin (95)                              Comp. Ex. 1-3                                                                          sorbitan monostearate (1)                                                                        liquid paraffin (99)                              Comp. Ex. 1-4                                                                          sorbitan monostearate (5)                                                                        liquid paraffin (95)                              Comp. Ex. 1-5                                                                          POE(10) hardened castor oil (10)                                                                 liquid paraffin (90)                              Comp. Ex. 1-6                                                                          POE(10) hardened castor oil (5)                                                                  liquid paraffin (95)                              ______________________________________                                    

                  TABLE 12                                                        ______________________________________                                        Evaluation of Emulsion Characteristics                                                                Emulsion                                                        Emulsion form stability                                             Outer oil phase                                                                           directly after preparation                                                                    RT    50° C.                               ______________________________________                                        Comp. Ex. 1-1                                                                             O/W/O           X     X                                           Comp. Ex. 1-2                                                                             O/W/O + O/W     X     X                                           Comp. Ex. 1-3                                                                             O/W/O           X     X                                           Comp. Ex. 1-4                                                                             O/W/O           X     X                                           Comp. Ex. 1-5                                                                             O/W/O + O/W     X     X                                           Comp. Ex. 1-6                                                                             O/W/O + O/W     X     X                                           ______________________________________                                    

When the evaluation of Examples shown in Table 10 and that ofComparative Examples shown in Table 12 are compared with each other, itcan be seen that Examples 2-1 to 2-4 of the present invention aresuperior in emulsification stability to Comparative Examples 1-1 to 1-6.

EXAMPLE 3

Further, the inventors studied the emulsification stability and agentstability when an oil-soluble agent was added in the emulsion. Here, asthe oil-soluble agent, retinol was used. Each of the preparation methodsin Table 13 to 16 was similar to Table 3 to 6 above, respectively.

                  TABLE 13                                                        ______________________________________                                        O/W Type Emulsion                                                                                      Example                                              Constituent              3-1                                                  ______________________________________                                        (a) Surfactant phase                                                          1,3-Butanediol           21                                                   Purified water            2                                                   POE(60) hardened castor oil                                                                             2                                                   (b) Oil phase                                                                 Liquid paraffin          32                                                   Retinol                   1                                                   (c) Water phase                                                               Purified water           42                                                   Emulsification stability (observation of the state)                           RT                       ◯                                        50° C.            ◯                                        Agent remaining ratio    X                                                    ______________________________________                                    

                  TABLE 14                                                        ______________________________________                                        W/O Type Emulsion                                                                          Example                                                          Constituent    3-2    3-3    3-4  3-5  3-6  3-7                               ______________________________________                                        (a) Surfactant                                                                POE(3) oleyl ether                                                                           1      --     --   --   --   --                                POE(2) oleyl ether                                                                           --     5      --   --   --   --                                Sorbitan monostearate                                                                        --     --     1    --   --   --                                Sorbitan monostearate                                                                        --     --     --   5    --   --                                POE(10) hardened castor oil                                                                  --     --     --   --   10   --                                POE(10) hardened castor oil                                                                  --     --     --   --   --   5                                 (b) Oil phase                                                                 Liquid paraffin                                                                              38     34     38   34   29   34                                Retinol        1      1      1    1    1    1                                 (c) Water phase                                                               Ion-exchanged water                                                                          60     60     60   60   60   60                                Emulsification stability                                                      (observation of the state)                                                    RT             ◯                                                                        ◯                                                                        ◯                                                                      ◯                                                                      ◯                                                                      ◯                     50° C.  ◯                                                                        ◯                                                                        ◯                                                                      ◯                                                                      ◯                                                                      ◯                     Agent remaining ratio                                                                        X      X      X    X    X    X                                 ______________________________________                                    

                  TABLE 15                                                        ______________________________________                                        O/W/O Type Emulsion                                                                        Example                                                          Constituent    3-8    3-9    3-10 3-11 3-12 3-13                              ______________________________________                                        (a) O/W phase                                                                 (containing retinol in                                                        oil phase)                                                                    O/W type emulsion                                                                            70     70     70   70   70   70                                of Example 3-1                                                                (b) Outer oil phase                                                           Liquid paraffin                                                                              29     25     29   25   20   25                                (c) Lipophilic surfactant                                                     POE(3) oleyl ether                                                                            1     --     --   --   --   --                                POE(2) oleyl ether                                                                           --      5     --   --   --   --                                Sorbitan monostearate                                                                        --     --      1   --   --   --                                Sorbitan monostearate                                                                        --     --     --    5   --   --                                POE(10) hardened castor oil                                                                  --     --     --   --   10   --                                POE(10) hardened castor oil                                                                  --     --     --   --   --    5                                Emulsification stability                                                      Observation of the state                                                      RT             X      X      X    X    X    X                                 50° C.  X      X      X    X    X    X                                 Inner oil phase remaining                                                                    <5     <5     <5   <5   <5   <5                                ratio (after 8 weeks at 50° C.)                                        Agent remaining ratio                                                                        X      X      X    X    X    X                                 ______________________________________                                    

                  TABLE 16                                                        ______________________________________                                        O/W/O type multiple emulsion                                                                  Example                                                       Constituent       3-14   3-15   3-16 3-17 3-18                                ______________________________________                                        (a) O/W phase (containing retinol                                             in oil phase)                                                                 O/W type emulsion 70     70     70   70   70                                  of Example 3-1                                                                (b) Outer oil phase                                                           Liquid paraffin   28     28     28   28   28                                  (c) Surfactant in outer oil phase                                             Organophilic clay mineral                                                                        2     --     --   --   --                                  (Preparation 1)                                                               Unmodified clay mineral(Beegum)                                                                 --      2     --   --   --                                  Benzyldimethylstearyl                                                                           --     --      2   --   --                                  ammonium chloride                                                             POE(6) lauryl ether                                                                             --     --     --    2   --                                  Benzyldimethylstearyl                                                                           --     --     --   --    2                                  ammonium chloride +                                                           POE(6) lauryl ether                                                           Emulsification stability                                                      Observation of the state                                                      RT                ◯                                                                        X      X    X    X                                   50° C.     ◯                                                                        X      X    X    X                                   Inner oil phase remaining ratio                                                                 98     <5     <5   <5   <5                                  (after 8 weeks at 50° C.)                                              Agent remaining ratio                                                                           ⊚                                                                     X      X    X    X                                   ______________________________________                                    

According to Tables 13 and 14, while a considerably high emulsificationstability can be attained in O/W type emulsions and W/O type emulsionsby selecting appropriate surfactants even when an oil-soluble agent iscompounded in their oil phase, their agent remaining ratio is quite low.Then, while a stable O/W emulsion was dispersed in the oil phase to forman O/W/O type emulsion in anticipation of an improved agent stability,the emulsification stability of thus obtained O/W/O emulsion was greatlydeteriorated, whereby the inner oil phase exuded into the outer oilphase. Thus, retinol added in the inner oil phase exuded into the outeroil phase, whereby anticipated stabilizing effects could not beobtained.

Contrary to this, as can be seen from Table 16, when the organophilicclay mineral was added in the outer oil phase, an emulsion which wasquite good in both of stability of the emulsification state and inneroil phase remaining ratio was obtained, and further the agent stabilityof retinol added in the inner oil phase was remarkably improved.

On the other hand, when the unmodified clay mineral,benzyldimethylstearyl ammonium chloride, and POE (6) lauryl ether, whichwere constituents of the organophilic clay mineral, were used separatelyor in combination, the high emulsification stability and agent stabilitysuch as those obtained when the organophilic clay was compounded couldnot be obtained.

Accordingly, when the stable O/W type emulsion is simply substituted fora water phase of the stable W/O type emulsion, the emulsificationstability of the multiple emulsion and the stability of the agent addedin the inner oil phase cannot be improved. Therefor, it is understoodthat such effects can be obtained specially only when the organophilicclay mineral is used.

EXAMPLE 4

A preferable composition in cases where an oil-soluble agent was addedin the inner oil phase was studied as follows:

(1) Composition

                  TABLE 17                                                        ______________________________________                                        Composition of O/W Type Emulsion                                              Constituent         Content                                                   ______________________________________                                        (a) Surfactant phase                                                          1,3-Butanediol      21                                                        Purified water       2                                                        POE(60) hardened castor oil                                                                        2                                                        (b) Inner oil phase                                                           Liquid paraffin     32                                                        Retinol              1                                                        (c) Water phase                                                               Purified water      42                                                        ______________________________________                                    

                  TABLE 18                                                        ______________________________________                                        Composition of Outer oil phase                                                Constituent        Content                                                    ______________________________________                                        (d) Surfactant                                                                Organophilic clay mineral                                                                         7                                                         of Preparation 1                                                              (e) Outer phase oil                                                           Liquid paraffin    93                                                         ______________________________________                                    

                  TABLE 19                                                        ______________________________________                                        Constitutional Ratio of O/W/O Type Multiple Emulsion                                   Amount of O/W type emulsion                                                                      Outer oil phase                                   Example  (parts by weight)  (parts by weight)                                 ______________________________________                                        Example 4-1                                                                            50                 50                                                Example 4-2                                                                            60                 40                                                Example 4-3                                                                            70                 30                                                Example 4-4                                                                            80                 20                                                Example 4-5                                                                            35                 65                                                Example 4-6                                                                            97                  3                                                ______________________________________                                    

(2) Method of preparation

The preparation method was similar to Example 2 above. Namely, first,into the mixture of uniformly dissolved ingredient (a) shown in Table17, ingredient (b) was mixed and emulsified while being stirred. Then,ingredient (c) was added thereto and mixed therewith to yield an O/Wtype emulsion.

Thereafter, the outer oil phase components shown in Table 18 were mixed.In this outer oil phase, the O/W type emulsion prepared above was mixedand emulsified while being stirred to yield the aimed O/W/O typemultiple emulsion. Here, the ratio of the O/W type emulsion to the outeroil phase was changed as shown in Table 19 to form Examples 4-1 to 4-6.

(3) Result

                  TABLE 20                                                        ______________________________________                                        Evaluation of Emulsion Characteristics                                                          Emulsifi-                                                          Emulsion form                                                                            cation    Inner oil Agent                                   Outer  directly after                                                                           stability phase     remaining                               oil phase                                                                            preparation                                                                              RT    50° C.                                                                       remaining ratio*                                                                        ratio                                 ______________________________________                                        Ex. 4-1                                                                              O/W/O      ◯                                                                       ◯                                                                        93%      ⊚                      Ex. 4-2                                                                              O/W/O      ⊚                                                                    ◯                                                                       96        ⊚                      Ex. 4-3                                                                              O/W/O      ⊚                                                                    ⊚                                                                    99        ⊚                      Ex. 4-4                                                                              O/W/O      ⊚                                                                    ◯                                                                       93        ⊚                      Ex. 4-5                                                                              O/W/O      X     X     --        X                                     Ex. 4-6                                                                              O/W/O + O/W                                                                              X     X     --        X                                     ______________________________________                                         *Inner oil remaining ratio was measured after the storage at 50° C     for one month.                                                           

As can be seen from Table 20, when the ratio of O/W type emulsion toouter oil phase is outside of the range of 2:3 to 19:1, stable multipleemulsions cannot be obtained and the stability of the agent (retinol)becomes quite unfavorable. Contrary to this, it can be understood that,when the ratio is within the range of 2:3 to 19:1, the system has afavorable emulsification stability and the stability of the agent addedin the inner oil phase can be remarkably improved.

EXAMPLE 5

O/W/O type emulsions were prepared in a manner similar to thepreparation method of the above-mentioned Example 4, while the amountsof the respective ingredients were changed according to theprescriptions shown in Tables 21 and 22. As a result, it was evidencedthat, as in the case of Table 20, the system has favorableemulsification stability and agent stability when the ratio of O/W typeemulsion to outer oil phase is within the range of 2:3 to 19:1 by weightratio.

                  TABLE 21                                                        ______________________________________                                        Study of Composition Ratio                                                                    Example                                                       Constituent       5-1    5-2    5-3  5-4  5-5                                 ______________________________________                                        (a) Surfactant                                                                1,3-Butyleneglycol                                                                              3      4      3    2    3                                   Glycerine         5      6      5    4    5                                   POE(60) hardened castor oil                                                                     1      1.2    1    0.8  1                                   Methyl paraben    0.15   0.15   0.15 0.15 0.15                                (b) Inner oil phase                                                           Squalane          5      5      5    5    5                                   Glyceryl tri-2-ethylhexanoate                                                                   5      10     5    2.5  5                                   Vitamin A palmitate                                                                             1      2      1    0.5  1                                   (c) Water phase                                                               Purified water    75.35  55.15  46.85                                                                              35.55                                                                              13.85                               (d) Outer oil phase                                                           Squalane          3      15     30   45   60                                  Cationic denatured clay mineral                                                                 0.5    0.5    1    1.5  2                                   (Benton-38)                                                                   POE(6) oleyl ether                                                                              1      1      2    3    4                                   O/W emulsion:outer oil phase                                                                    21:1   5:1    2:1  1:1  0.5:1                               (weight ratio)                                                                Emulsification stability                                                      (observation of the state)                                                    50° C.     X      ◯                                                                        ⊚                                                                   ◯                                                                      X                                   Remaining ratio of vitamin                                                                      X      ⊚                                                                     ⊚                                                                   ⊚                                                                   X                                   A palmitate                                                                   ______________________________________                                    

                  TABLE 22                                                        ______________________________________                                                        Example                                                       Constituent       5-6    5-7    5-8  5-9  5-10                                ______________________________________                                        (a) Surfactant                                                                1,3-Butyleneglycol                                                                              3      4      3    2    3                                   Glycerine         5      6      5    4    5                                   POE(60) hardened castor oil                                                                     1      1.2    1    0.8  1                                   Methyl paraben    0.15   0.15   0.15 0.15 0.15                                (b) Inner oil phase                                                           Octyl methoxycinnamate                                                                          5      5      5    5    5                                   Glyceryl tri-2-ethylhexanoate                                                                   5      10     5    2.5  5                                   Octyl dimethyl PABA*                                                                            1      2      1    0.5  1                                   (c) Water phase                                                               Purified water    75.35  55.15  46.85                                                                              35.55                                                                              13.85                               (d) Outer oil phase                                                           Liquid paraffin   1.5    7.5    15   22.5 30                                  Isoparaffin       1.5    7.5    15   22.5 30                                  Cationic denatured clay mineral                                                                 0.5    0.5    1    1.5  2                                   (Benton-38)                                                                   POE(10) oleyl ether                                                                             1      1      2    3    4                                   O/W emulsion:outer oil phase                                                                    21:1   5:1    2:1  1:1  0.5:1                               (weight ratio)                                                                Emulsification stability                                                      (observation of the state)                                                    50° C.     X      ◯                                                                        ⊚                                                                   ◯                                                                      X                                   Remaining ratio   X      ⊚                                                                     ⊚                                                                   ⊚                                                                   X                                   of Octyl dimethyl PABA                                                        ______________________________________                                         *Octyl dimethyl PABA; Octyl pdimethylaminobenzoate.                      

EXAMPLE 6 AND COMPARATIVE EXAMPLE 2 TO 3

Next, O/W/O type and W/O type emulsions were prepared according toprescriptions shown in Table 23 and their agent stability was studiedwhile the oil-soluble agent added in their inner oil phase was changed.

(1) Composition

                  TABLE 23                                                        ______________________________________                                                        Ex. 6    Comp. Ex. 2                                                                             Comp. Ex. 3                                Constituent     (O/W/O)  (W/O)     (O/W/O)                                    ______________________________________                                        (a) Surfactant phase                                                          1,3-Butyleneglycol                                                                            5        5         5                                          POE(60) hardened castor oil                                                                   1        --        --                                         Bentonite       --       --        0.5                                        Methyl paraben  0.1      0.1       0.1                                        (b) Inner oil phase                                                           Squalane        5        --        5                                          Pentaerythritol 5        --        5                                          tetra-2-ethylhexanoate                                                        Cetanol         --       --        3                                          POE(20) sorbitan tristearate                                                                  --       --        1                                          Diglycenne monooleate                                                                         --       --        2                                          Oil-soluble vitamin(cf. Table 24)                                                             1        --        1                                          (c) Water phase                                                               Purified water  49.9     50.9      37.4                                       (d) Outer oil phase                                                           Liquid paraffin 30       30        30                                         Organophilic clay mineral                                                                     1        1         1                                          (Preparation 1)                                                               POE(6) oleyl ether                                                                            2        2         --                                         Squalane        --       5         --                                         Pentaerythritol --       5         --                                         tetra-2-ethylhexanoate                                                        Dextrin palmitate                                                                             --       --        1                                          Cetanol         --       --        3                                          Beeswax         --       --        2                                          Sorbitan sesquioleate                                                                         --       --        3                                          Sorbitan monostearate                                                                         --       --        1                                          Oil-soluble vitamin(cf. Table 24)                                                             --       1         --                                         ______________________________________                                    

(2) Method of Preparation

EXAMPLE 6

To a mixture of uniformly dissolved ingredient (a), ingredient (b) wasmixed while being stirred, and the obtained mixture was dispersed andemulsified to yield an oil in surfactant phase type emulsioncomposition. Then, ingredient (c) was added thereto and mixed therewithto obtain an O/W type emulsion. Thus O/W type emulsion was mixed andemulsified in ingredient (d) which had been mixed and dispersedbeforehand, thereby yielding the aimed O/W/O type multiple emulsion.

COMPARATIVE EXAMPLE 2

After ingredient (a) were uniformly dissolved and mixed, ingredients (a)and (c) were mixed. While being stirred, ingredient (a)+(c) was mixedand emulsified in ingredient (d), thereby yielding the aimed W/O typemultiple emulsion.

COMPARATIVE EXAMPLE 3

After ingredient (a)+(c) and ingredient (d) were separately heated andmelted at 70° C., ingredient (b) was mixed, dispersed, and emulsified iningredient (a)+(c) while being stirred, thereby yielding an O/W typeemulsion. Then, this O/W type emulsion was mixed in ingredient (d),which had been heated and melted at 80° C. beforehand while beingstirred, and then cooled to 30° C. while being stirred, thereby yieldingthe aimed O/W/O type multiple emulsion.

(3) Method of Evaluation

The emulsification stability and agent remaining ratio of thus preparedemulsion were evaluated in the above-mentioned manner. Also, discoloringand change in odor of the emulsion after being kept at 50° C. in anincubator for one month were judged and evaluated according to thefollowing standards.

Discoloring (by visual judgment)

⊚: no discoloring

O: slight discoloring

Δ: considerable discoloring

X: remarkable discoloring

Change in odor

⊚: no change

O: little change

Δ: slight offensive odor

X: remarkable offensive odor

(4) Result

                                      TABLE 24                                    __________________________________________________________________________    Evaluation of Emulsion Characteristics                                                         Emulsification stability                                                                    Remaining ratio                                Example Oil-soluble vitamin                                                                    Discoloring                                                                          Odor                                                                             State                                                                             of Vitamin(%)                                  __________________________________________________________________________    Example                                                                            6-1                                                                              retinol  ⊚                                                                     ⊚                                                                 ◯                                                                     90.5                                           (O/W/O)                                                                            6-2                                                                              vitamin A palmitate                                                                    ⊚                                                                     ⊚                                                                 ◯                                                                     98.1                                                6-3                                                                              vitamin A acetate                                                                      ⊚                                                                     ⊚                                                                 ◯                                                                     97.8                                                6-4                                                                              α-tocopherol                                                                     ⊚                                                                     ⊚                                                                 ◯                                                                     97.2                                                6-5                                                                              vitamin E acetate                                                                      ⊚                                                                     ⊚                                                                 ◯                                                                     100.2                                               6-6                                                                              vitamin D.sub.2                                                                        ⊚                                                                     ⊚                                                                 ◯                                                                     99.5                                                6-7                                                                              β-carotene                                                                        ⊚                                                                     ⊚                                                                 ◯                                                                     96.5                                           Comp. Ex.                                                                          2-1                                                                              retinol  X      X  ◯                                                                     65.0                                           (W/O)                                                                              2-2                                                                              vitamin A palmitate                                                                    Δ                                                                              Δ                                                                          ◯                                                                     70.1                                                2-3                                                                              vitamin Acetate                                                                        Δ                                                                              Δ                                                                          ◯                                                                     74.9                                                2-4                                                                              α-tocopherol                                                                     Δ                                                                              ◯                                                                    ◯                                                                     69.9                                                2-5                                                                              vitamin E acetate                                                                      ◯                                                                        ◯                                                                    ◯                                                                     80.1                                                2-6                                                                              vitamin D.sub.2                                                                        Δ                                                                              ◯                                                                    ◯                                                                     83.8                                                2-7                                                                              β-carotene                                                                        Δ                                                                              ◯                                                                    ◯                                                                     79.8                                           Comp. Ex.                                                                          3-1                                                                              retinol  X      X  X   17.2                                           (O/W/O)                                                                            3-2                                                                              vitamin A palmitate                                                                    X      X  X   36.6                                                3-3                                                                              vitamin A acetate                                                                      X      X  X   40.8                                                3-4                                                                              α-tocopherol                                                                     Δ                                                                              Δ                                                                          X   66.7                                                3-5                                                                              vitamin E acetate                                                                      Δ                                                                              Δ                                                                          X   78.9                                                3-6                                                                              vitamin D.sub.2                                                                        Δ                                                                              Δ                                                                          X   80.7                                                3-7                                                                              β-carotene                                                                        Δ                                                                              ◯                                                                    Δ                                                                           77.7                                           __________________________________________________________________________

As can be seen from Table 24, the O/W/O type emulsions (Examples 6-1 to6-7) in which an organophilic clay mineral had been added in the outeroil phase were excellent in emulsification stability without separationof oil or the like, discoloring, and change in odor and exhibited aremarkably high agent remaining ratio.

In the W/O type emulsions of Comparative Examples 2-1 to 2-7, on theother hand, while stable emulsification conditions were obtained withoutnoticeable separation of the oil phase or the like, since the agent(oil-soluble vitamin) was added in the outer oil phase, the remainingratio of the agent was remarkably decreased due to the oxidativedecomposition. Also, in the O/W/O type multiple emulsions prepared bythe conventional technique such as those of Comparative Examples 3-1 to3-7, their emulsification stability was so low that they were easilyseparated and, since its preparation step was accompanied by heating,the decomposition of the agent added in the inner oil phase wasremarkable and the degree of discoloring and change in odor was greatalso.

EXAMPLE 7 AND COMPARATIVE EXAMPLE 4

O/W/O type or W/O type emulsions in which various kinds of oil-solubleultraviolet absorbers were added in the inner oil phase were preparedaccording to the prescription shown in Table 25 and their emulsificationstabilities were studied.

(1) Composition

                  TABLE 25                                                        ______________________________________                                                            Ex. 7    Comp. Ex. 4                                      Constituent         (O/W/O)  (W/O)                                            ______________________________________                                        (a) Surfactant phase                                                          1,3-Butyleneglycol  5        5                                                POE(60) hardened castor oil                                                                       1        --                                               Methyl paraben      0.1      0.1                                              (b) Inner oil phase                                                           Squalane            5        --                                               Pentaerythritol     5        --                                               tetra-2-ethylhexanoate                                                        Ultraviolet absorber(cf. Table 26)                                                                2        --                                               (c) Water phase                                                               Purified water      48.9     59.9                                             (d) Outer oil phase                                                           Liquid paraffin     30       30                                               Organophilic clay mineral                                                                         1        1                                                of Preparation 1                                                              POE(6) stearyl ether                                                                              2        2                                                Ultraviolet absorber(cf. Table 26)                                                                --       2                                                ______________________________________                                    

(2) Method of preparation

EXAMPLE 7

It was prepared in a manner similar to Example 6.

COMPARATIVE EXAMPLE 4

It was prepared in a manner similar to Comparative Example 2.

(3) Method of evaluation

With respect to the emulsions shown in Table 25, observation of theemulsified state was performed by the above-mentioned method, wherebychanges in emulsification conditions such as change in particle size,separation, and discoloring were inspected so as to evaluate theemulsification stability. Here, the storage period was six months at 25°C. or two months at 50° C.

(4) Result

                                      TABLE 26                                    __________________________________________________________________________    Emulsification Stability                                                      Example Ultraviolet absorber                                                                              Emulsification stability                          __________________________________________________________________________    Example                                                                            7-1                                                                              2,4-dihydroxybenzophenone                                                                         ⊚                                  (O/W/O)                                                                            7-2                                                                              2,2'-dihydroxy-4-methoxybenzophenone                                                              ⊚                                       7-3                                                                              2,2'-dihydroxy-4,4-dimethoxybenzophenone                                                          ⊚                                       7-4                                                                              2,2',4,4'-tetrahydroxybenzophenone                                                                ⊚                                       7-5                                                                              2-hydroxy-4-methoxybenzophenone                                                                   ⊚                                       7-6                                                                              2-hydroxy-4-methoxy-4'-methylbenzopheone                                                          ⊚                                       7-7                                                                              3-(4-methylbenzylidene)-d,1-camphor                                                               ⊚                                       7-8                                                                              3-benzylidene-d,1-camphor                                                                         ⊚                                       7-9                                                                              4-methoxy-4'-t-butyldibenzoylmethane                                                              ⊚                                  Comp. Ex.                                                                          4-1                                                                              2,4-dihydroxybenzophenone                                                                         X                                                 (W/O)                                                                              4-2                                                                              2,2'-dihydroxy-4-methoxybenzophenone                                                              X                                                      4-3                                                                              2,2'-dihydroxy-4,4-dimethoxybenzophenone                                                          X                                                      4-4                                                                              2,2',4,4'-tetrahydroxybenzophenone                                                                X                                                      4-5                                                                              2-hydroxy-4-methoxybenzophenone                                                                   X                                                      4-6                                                                              2-hydroxy-4-methoxy-4'-methylbenzophenone                                                         X                                                      4-7                                                                              3-(4-methylbenzylidene)-d,1-camphor                                                               X                                                      4-8                                                                              3-benzylidene-d,1-camphor                                                                         X                                                      4-9                                                                              4-methoxy-4'-t-butyldibenzoylmethane                                                              X                                                 __________________________________________________________________________

As can be seen from Table 26, while discoloring, separation of oil, orthe like were recognized in the W/O type emulsions of ComparativeExamples since the ultraviolet absorbers were contained in the outer oilphase which comes into direct contact with the air, emulsion stabilitywas favorable in any of Examples.

Thus, suncare cosmetic preparations having excellent emulsificationstability can be made by using the O/W/O type emulsion in accordancewith the present invention.

EXAMPLE 8 AND COMPARATIVE EXAMPLE 5 TO 6

Next, O/W/O type and W/O type emulsions were prepared according toprescriptions shown in Table 27 and their agent stability was studiedwhile the unsaturated fatty acids added in their inner oil phase waschanged.

(1) Composition

                  TABLE 27                                                        ______________________________________                                                       Ex. 8     Comp. Ex. 5                                                                             Comp. Ex. 6                                Constituent    (O/W/O)   (W/O)     (O/W)                                      ______________________________________                                        (a) Surfactant phase                                                          1,3-Butyleneglycol                                                                           10        10        10                                         POE(60) hardened castor oil                                                                  1         --        1                                          Methyl paraben 0.1       0.1       0.1                                        (b) Inner oil phase                                                           Liquid paraffin                                                                              5         --        5                                          Pentaerythritol                                                                              5         --        5                                          tetra-2-ethylhexanoate                                                        Cetanol        --        --        2                                          Unsaturated fatty acid                                                                       1         --        1                                          (cf. Table 28)                                                                (c) Water phase                                                               Purified water 46.9      57.9      75.9                                       (d) Outer oil phase                                                           Liquid paraffin                                                                              10        10        --                                         Isoparaffin    10        10        --                                         Squalane       10        10        --                                         Organophilic clay mineral                                                                    1         1         --                                         (Preparation 1)                                                               Unsaturated fatty acid                                                                       --        1         --                                         (cf. Table 28)                                                                ______________________________________                                    

(2) Method of preparation

EXAMPLE 8

It was prepared in a manner similar to Example 6.

COMPARATIVE EXAMPLE 5

It was prepared in a manner similar to Comparative Example 2.

COMPARATIVE EXAMPLE 6

To a mixture of uniformly dissolved ingredient (a), ingredient (b) wasmixed while being stirred, and the obtained mixture was dispersed andemulsified to yield an oil in surfactant phase type emulsioncomposition. Then, ingredient (c) was added therein and mixed to yieldthe O/W type emulsion.

(3) Method of evaluation

It was evaluated in a manner similar to Example 6.

(4) Result

                                      TABLE 28                                    __________________________________________________________________________    Evaluation of Emulsion Characteristics                                                Unsaturated                                                                            Emulsification stability                                                                    Remaining ratio                                Example fatty acid                                                                             Discoloring                                                                          Odor                                                                             State                                                                             of Vitamin(%)                                  __________________________________________________________________________    Example                                                                            8-1                                                                              γ-linolenic acid                                                                 ⊚                                                                     ⊚                                                                 ◯                                                                     98.1                                           (O/W/O)                                                                            8-2                                                                              arachidonic acid                                                                       ⊚                                                                     ⊚                                                                 ◯                                                                     94.5                                                8-3                                                                              eicosapentaenic acid                                                                   ⊚                                                                     ⊚                                                                 ◯                                                                     92.1                                                8-4                                                                              docosahexaenic                                                                         ⊚                                                                     ⊚                                                                 ◯                                                                     90.2                                                   acid                                                                       8-5                                                                              methyl   ⊚                                                                     ⊚                                                                 ◯                                                                     97.8                                                   docosahexaenate                                                            8-6                                                                              ethyl    ⊚                                                                     ⊚                                                                 ◯                                                                     99.2                                                   docosahexaenate                                                       Comp. Ex.                                                                          5-1                                                                              γ-linolenic acid                                                                 ◯                                                                        Δ                                                                          ⊚                                                                  60.9                                           (W/O)                                                                              5-2                                                                              arachidonic acid                                                                       Δ                                                                              Δ                                                                          ◯                                                                     52.5                                                5-3                                                                              eicosapentaenic acid                                                                   X      X  ◯                                                                     48.8                                                5-4                                                                              docosahexaenic                                                                         X      X  ◯                                                                     45.2                                                   acid                                                                       5-5                                                                              methyl   X      X  ◯                                                                     58.4                                                   docosahexaenate                                                            5-6                                                                              ethyl    X      X  ⊚                                                                  63.3                                                   docosahexaenate                                                       Comp. Ex.                                                                          6-1                                                                              γ-linolenic acid                                                                 ◯                                                                        Δ                                                                          ⊚                                                                  52.1                                           (O/W)                                                                              6-2                                                                              arachidonic acid                                                                       Δ                                                                              X  ⊚                                                                  42.3                                                6-3                                                                              eicosapentaenic acid                                                                   Δ                                                                              X  ◯                                                                     40.6                                                6-4                                                                              docosahexaenic                                                                         X      X  ◯                                                                     32.7                                                   acid                                                                       6-5                                                                              methyl   X      X  ◯                                                                     68.4                                                   docosahexaenate                                                            6-6                                                                              ethyl    Δ                                                                              X  ◯                                                                     65.7                                                   docosahexaenate                                                       __________________________________________________________________________

As can be seen from Table 28, the O/W/O type emulsions (Examples 8-1 to8-6) in which an organophilic clay mineral had been added in the outeroil phase were excellent in emulsification stability without separationof oil or the like, discoloring, and change in odor and exhibited aremarkably high agent remaining ratio.

In the W/O type emulsions of Comparative Examples 5-1 to 5-6, on theother hand, while stable emulsification conditions were obtained withoutnoticeable separation of the oil phase or the like, since the agent(unsaturated fatty acid) was added in the outer oil phase, the remainingratio of the agent was remarkably decreased due to the oxidativedecomposition.

Also, in the O/W type emulsions of Comparative Examples 6-1 to 6-6,while stable emulsification conditions were obtained, agent stabilitywas low and the degree of discoloring and change in odor was remarkablealso.

EXAMPLE 9

Next, the emulsion in which a silicone type oil was added in the oilphase has been studied. Here, each of the preparation methods in Table29 to 32 was similar to Table 3 to 6 above, respectively.

                  TABLE 29                                                        ______________________________________                                        O/W Type Emulsion                                                                                Example                                                    Constituent        9-1                                                        ______________________________________                                        (a) Surfactant phase                                                          1,3-Butanediol     21                                                         Purified water      2                                                         POE(60) hardened castor oil                                                                       2                                                         (b) Oil phase                                                                 Liquid paraffin    32                                                         (c) Water phase                                                               Purified water     42                                                         Emulsification stability                                                      (observation of the state)                                                    RT                 ◯                                              50° C.      ◯                                              Feel of use        X                                                          ______________________________________                                    

                  TABLE 30                                                        ______________________________________                                        W/O Type Emulsion                                                                              Example                                                      Constituent        9-2    9-3   9-4 9-5 9-6 9-7                               ______________________________________                                        (a) Surfactant                                                                POE methylpolysiloxane copolymer*1                                                                1      5    10  --  --  --                                POE methylpolysiloxane copolymer*2                                                               --     --    --   1   5  10                                (b) Oil phase                                                                 Decamethylcyclopentasiloxane                                                                     38     34    38  34  29  34                                Octamethylcyclotetrasiloxane                                                                      1      1     1   1   1   1                                (c) Water phase                                                               Ion-exchanged water                                                                              60     60    60  60  60  60                                Emulsification stability                                                      (observation of the state)                                                    RT                 ◯                                                                        ◯                                                                       ◯                                                                     ◯                                                                     ◯                                                                     ◯                     50° C.      ◯                                                                        ◯                                                                       ◯                                                                     ◯                                                                     ◯                                                                     ◯                     Feel of use        ◯                                                                        ◯                                                                       ◯                                                                     ◯                                                                     ◯                                                                     ◯                     ______________________________________                                    

                  TABLE 31                                                        ______________________________________                                        O/W/O Type Emulsion                                                                          Example                                                        Constituent      9-8   9-9   9-10 9-11 9-12 9-13                              ______________________________________                                        (a) O/W phase                                                                 O/W type emulsion of                                                                           70    70    70   70   70   70                                Example 9-1                                                                   (b) Outer oil phase                                                           Decamethylcyclopentasiloxane                                                                   29    25    20   --   --   --                                Octamethylcyclotetrasiloxane                                                                   --    --    --   29   25   20                                (c) Lipophilic surfactant                                                     POE methylpolysiloxane                                                                          1     5    10   --   --   --                                copolymer*1                                                                   POE methylpolysiloxane                                                                         --    --    --    1    5   10                                copolymer*2                                                                   Emulsification stability                                                      Observation of the state                                                      RT               X     X     X    X    X    X                                 50° C.    X     X     X    X    X    X                                 Inner oil phase remaining                                                                      <5    <5    <5   <5   <5   <5                                ratio (after 8 weeks at 50° C.)                                        Feel of use      Δ                                                                             Δ                                                                             Δ                                                                            Δ                                                                            Δ                                                                            Δ                           ______________________________________                                         *1 and *2 are the same as those in Table 30.                             

                  TABLE 32                                                        ______________________________________                                        O/W/O type multiple emulsion                                                                  Example                                                       Constituent       9-14   9-15   9-16 9-17 9-18                                ______________________________________                                        (a) O/W phase                                                                 O/W type emulsion of                                                                            70     70     70   70   70                                  Example 9-1                                                                   (b) Outer oil phase                                                           Decamethylcyclopentasiloxane                                                                    28     28     28   28   28                                  Surfactant in outer oil phase                                                 Organophilic clay mineral*                                                                       2     --     --   --   --                                  Unmodified clay mineral(Beegum)                                                                 --      2     --   --   --                                  Benzyldimethylstearyl ammonium                                                                  --     --      2   --   --                                  chloride                                                                      POE methylpolysiloxane                                                                          --     --     --    2   --                                  copolymer**                                                                   Benzyldimethylstearyl ammonium                                                                  --     --     --   --    2                                  chloride +                                                                    POE methylpolysiloxane                                                        copolymer**                                                                   Emulsification stability                                                      Observation of the state                                                      RT                ◯                                                                        X      X    X    X                                   50° C.     ◯                                                                        X      X    X    X                                   Inner oil phase remaining                                                                       98     <5     <5   <5   <5                                  ratio (after 8 weeks at 50° C.)                                        Feel of use       ⊚                                                                     ◯                                                                        ◯                                                                      ◯                                                                      ◯                       ______________________________________                                         *This organophilic clay mineral was prepared in a manner similar to           Preparation 1 except for using POE methylpolysiloxane copolymer Silicone      SC9450N, manufactured by SINETSU KAGAKU KOGYO Co., Ltd., in stead of          POE(6) lauryl ether.                                                          **The product name is Silicone SC9450N(manufactured by SINETSU KAGAKU         KOGYO Co., Ltd.).                                                        

According to Tables 29 and 30, a considerably high emulsificationstability can be attained in O/W type emulsions and W/O type emulsionsby selecting appropriate surfactants. However, when such a stable O/Wemulsion was dispersed in the outer oil phase containing a silicone typeoil to form an O/W/O type emulsion, the emulsification stability of thusobtained O/W/O emulsion was greatly deteriorated, whereby the inner oilphase exuded into the outer oil phase.

Contrary to this, as can be seen from Table 32, even when theorganophilic clay mineral was added in the outer oil phase of O/W/Omultiple emulsion containing a silicone type oil, an emulsificationstability was quite good in both observation of the emulsification stateand inner oil phase remaining ratio to be excellent.

Also, in the multiple emulsion of Example 9-14, which contained asilicone type oil and an organophilic clay mineral, when it applied onskin, good spreadability and lack of greasiness were exhibited so thatthe feel of use was quite excellent as compared with those of both ofW/O type emulsion using a silicone type oil in Table 30 and the multipleemulsion in Table 31.

Here, when octamethylcyclotetrasiloxane was used in stead ofdecamethylcyclopentasiloxane in Table 32, the same result has beenobtained.

Contrary to this, as can be seen from Table 32, even when theorganophilic clay mineral was added in the outer oil phase of O/W/Ocontaining a silicone type oil, an emulsion which was quite good in bothof stability of the emulsification state and inner oil phase remainingratio was obtained, and further the agent stability of retinol added inthe inner oil phase was remarkably improved.

Accordingly, when the stable O/W type emulsion is simply substituted fora water phase of the stable W/O type emulsion, a stable multipleemulsion containing a silicone type oil can not be obtained. Therefor,even if each of silicone type oils and non-silicone type oils is addedin separate oil phases at the time of preparation, these can not be keepstable.

On the other hand, when an organophilic clay mineral is added in theouter oil phase, as coalescence between the inner oil phase and theouter oil phase are suppressed, a stable multiple emulsion containing asilicone type oil can be obtained. And then, when each of silicone typeoils and non-silicone type oils is added in separate oil phases at thetime of preparation, these can be keep stable independently. Also, thefeel of use is very excellent as compared with a W/O type emulsioncontaining a silicone type oil.

EXAMPLE 10

As explained in the following, in such a multiple emulsion, effects forpreventing crystals from depositing were inspected, while4-tert-butyl-4'-methoxydibenzoylmethane, which is a kind of ultravioletabsorber, was used as an oil-soluble agent which was hard to dissolve ina silicone type oil. Also, its feel of use was studied. Here, themethods of preparing the emulsions in the following Tables 33 to 36 werebased on those in the above-mentioned Tables 3 to 6, respectively.

                  TABLE 33                                                        ______________________________________                                        O/W Type Emulsion                                                                                    Example                                                Constituent            10-1                                                   ______________________________________                                        (a) Surfactant phase                                                          1,3-Butanediol         21                                                     Purified water          2                                                     POE(60) hardened castor oil                                                                           2                                                     (b) Oil phase                                                                 Dioctyl succinate      31                                                     4-tert-butyl-4'-methoxydibenzoylmethane                                                               2                                                     (c) Water phase                                                               Purified water         42                                                     Emulsification stability                                                      (observation of the state)                                                    RT                     ◯                                          50° C.          ◯                                          Crystal deposit        ◯                                                                 (none)                                                 Feel of use            X                                                      ______________________________________                                    

                  TABLE 34                                                        ______________________________________                                        W/O Type Emulsion                                                                                Example                                                    Constituent          10-2      10-3                                           ______________________________________                                        (a) Surfactant                                                                POE methylpolysiloxane copolymer                                                                    5         5                                             (b) Oil phase                                                                 Decamethylcyclopentasiloxane                                                                       33        --                                             Octamethylcyclotetrasiloxane                                                                       --        33                                             4-tert-butyl-4'-methoxydibenzoylmethane                                                             2         2                                             (c) Water phase                                                               Ion-exchanged water  60        60                                             Emulsification stability                                                      (observation of the state)                                                    RT                   ◯                                                                           ◯                                  50° C.        ◯                                                                           ◯                                  Crystal deposit      X (deposit)                                                                             X (deposit)                                    Feel of use          ◯                                                                           ◯                                  ______________________________________                                         *The product name is Silicone SC9450N(manufactured by SINETSU KAGAKU KOGY     Co., Ltd.).                                                              

                  TABLE 35                                                        ______________________________________                                        O/W/O Type Emulsion                                                                              Example                                                    Constituent          10-4      10-5                                           ______________________________________                                        (a) O/W phase containing 4-tert-butyl-4'-                                     methoxydibenzoylmethane in oil phase)                                         O/W type emulsion of Example 10-1                                                                  70        70                                             (b) Outer oil phase                                                           Decamethylcyclopentasiloxane                                                                       25        --                                             Octamethylcyclotetrasiloxane                                                                       --        25                                             (c) Lipophilic surfactant                                                     POE methylpolysiloxane copolymer*                                                                   5         5                                             Emulsification stability                                                      Observation of the state                                                      RT                   X         X                                              50° C.        X         X                                              Inner oil phase remaining ratio                                                                    <5        <5                                             (after 8 weeks at 50° C.)                                              Crystal deposit      X (deposit)                                                                             X (deposit)                                    Feel of use          Δ   Δ                                        ______________________________________                                         *The product name is Silicone SC9450N (Manufactured by SINETSU KAGAKU         KOGYO Co., Ltd.).                                                        

                  TABLE 36                                                        ______________________________________                                        O/W/O type multiple emulsion                                                                     Example                                                    Constituent          10-6      10-7                                           ______________________________________                                        (a) O/W phase(containing 4-tert-butyl-4'-methoxydibenzoylmethane              in oil phase)                                                                 O/W type emulsion of Example 10-1                                                                  70        70                                             (b) Outer oil phase                                                           Decamethylcyclopentasiloxane                                                                       28        --                                             Octamethylcyclotetrasiloxane                                                                       --        28                                             (c) Lipophilic surfactant                                                     Organophilic clay mineral*                                                                          2         2                                             Emulsification stability                                                      Observation of the state                                                      RT                   ◯                                                                           ◯                                  50° C.        ◯                                                                           ◯                                  Inner oil phase remaining ratio                                                                    98        98                                             (after 8 weeks at 50° C.)                                              Crystal deposit      ◯(none)                                                                     ◯(none)                            Feel of use          Δ   Δ                                        ______________________________________                                         *This was the same as that used in Table 32.                             

As can be seen from the above-mentioned Tables 33 and 34, O/W type andW/O type emulsions with a high emulsion stability can also be obtainedwhen an oil-soluble agent (4-tert-butyl-4'-methoxydibenzoylmethane) isadded in the oil phase. Nevertheless, when a silicone type oil is notadded, their feel of use becomes inferior though no deposition of agentis seen; whereas, when the silicone type oil is added, deposition of theagent is seen over time though the feel of use improves.

Also, when the stable O/W type emulsion of Table 33 was dispersed in anoil phase containing a silicone type oil to prepare an O/W/O typeemulsion in expectation of attaining the feel of use of the siliconetype oil content and the effects for preventing crystals of the agentfrom depositing, its emulsion stability decreased so much that the inneroil phase exuded into the outer oil phase. As a result, the expectedeffects for preventing crystals of the agent from depositing could notbe obtained. Also, the feel of use tended to deteriorate.

By contrast, when an organophilic clay mineral was added in the outeroil phase as shown in the above-mentioned Table 36, the emulsionstability was quite favorable in terms of both emulsion state and inneroil phase remaining ratio. Also, in this multiple emulsion, sincecoalescence of the inner phase and outer oil phase was suppressed, theslightly soluble agent(4-tert-butyl-4'-methoxydibenzoylmethane) added inthe inner oil phase hardly came into contact with the silicone type oilin the outer oil phase and did not migrate to the outer oil phase,thereby effectively preventing crystals of the ultraviolet absorber fromdepositing. Also, its feel of use was free of greasiness and quitefavorable.

As explained in the foregoing, in the multiple emulsion of the presentinvention, as an organophilic clay mineral is provided in the outer oilphase, coalescence of the inner oil phase and outer oil phase issuppressed even when a silicone type oil is added therein, whereby ahigh emulsion stability can be obtained. Accordingly, the inner oilphase and the outer oil phase can stably coexist in a single phaseindependently from each other. Therefore, for example, when a materialwhich is hard to dissolve in a silicone type oil and a non-silicone typeoil are added in one oil phase whereas the silicone type oil is added inthe other oil phase, there can be obtained an emulsion which can preventthe material from depositing, while these ingredients stably coexist ina single system, and whose feel of use is quite excellent.

EXAMPLE 11

A preferable composition in a multiple emulsion containing aslightly-soluble agent to a silicone type oil and a silicone type oilwas studied as follows:

(1) Composition

                  TABLE 37                                                        ______________________________________                                        Composition of O/W Type Emulsion                                              Constituent            Content                                                ______________________________________                                        (a) Surfactant phase                                                          1,3-Butanediol         21                                                     Purified water          2                                                     POE(60) hardened castor oil                                                                           2                                                     (b) Inner oil phase                                                           Dioctyl succinate      31                                                     4-tert-butyl-4'-methoxydibenzoylmethane                                                               2                                                     (c) Water phase                                                               Purified water         42                                                     ______________________________________                                    

                  TABLE 38                                                        ______________________________________                                        Composition of Outer oil phase                                                Constituent            Content                                                ______________________________________                                        (d) Surfactant                                                                Organophilic clay mineral(Preparation 1)                                                              7                                                     (e) Outer phase oil                                                           Decamethylcyclopentasiloxane                                                                         93                                                     ______________________________________                                    

                  TABLE 39                                                        ______________________________________                                        Constitutional Ratio of O/W/O Type Multiple Emulsion                                    Amount of O/W type emulsion                                                                     Outer oil phase                                   Example   (parts by weight) (parts by weight)                                 ______________________________________                                        Example 11-1                                                                            50                50                                                Example 11-2                                                                            60                40                                                Example 11-3                                                                            70                30                                                Example 11-4                                                                            80                20                                                Example 11-5                                                                            35                65                                                Example 11-6                                                                            97                3                                                 ______________________________________                                    

(2) Method of preparation

The preparation method was similar to Example 2 above. Namely, first,into the mixture of uniformly dissolved ingredient (a) shown in Table37, ingredient (b) was mixed and emulsified while being stirred. Then,ingredient (c) was added thereto and mixed therewith to yield an O/Wtype emulsion.

Thereafter, the outer oil phase components shown in Table 38 were mixed.In this outer oil phase, the O/W type emulsion prepared above was mixedand emulsified while being stirred to yield the aimed O/W/O typemultiple emulsion. Here, the ratio of the O/W type emulsion to the outeroil phase was changed as shown in Table 39 to form Examples 11-1 to11-6.

(3) Result

                  TABLE 40                                                        ______________________________________                                        Evaluation of Emulsion Characteristics                                                          Emulsifi-                                                          Emulsion form                                                                            cation    Inner oil                                         Outer  directly after                                                                           stability phase     Crystal                                 oil phase                                                                            preparation                                                                              RT    50° C.                                                                       remaining ratio*                                                                        deposit                               ______________________________________                                        Ex. 11-1                                                                             O/W/O      ◯                                                                       ◯                                                                        92%      ◯(none)                   Ex. 11-2                                                                             O/W/O      ⊚                                                                    ◯                                                                       93        ◯(none)                   Ex. 11-3                                                                             O/W/O      ⊚                                                                    ⊚                                                                    98        ◯(none)                   Ex. 11-4                                                                             O/W/O      ⊚                                                                    ◯                                                                       93        ◯(none)                   Ex. 11-5                                                                             O/W/O      X     X     --        X(deposit)                            Ex. 11-6                                                                             O/W/O + O/W                                                                              X     X     --        X(deposit)                            ______________________________________                                         *Inner oil remaining ratio was measured after the storage at 50° C     for one month.                                                           

As could be seen from Table 40, when the ratio of O/W type emulsion toouter oil phase is outside of the range of 2:3 to 19:1, stable multipleemulsions could not be obtained and crystal deposit of the agent addedin the inner oil phase(4-tert-butyl-4'-methoxydibenzoylmethane) wasobserved. Contrary to this, it can be understood that, when the ratio iswithin the range of 2:3 to 19:1, the system has a favorableemulsification stability and crystal deposit of the agent added in theinner oil phase can be prevented.

EXAMPLE 12 AND COMPARATIVE EXAMPLE 7 TO 8

Next, O/W/O type and W/O type emulsions were prepared according toprescriptions shown in Table 41 and their effects on prevention of thecrystal deposit was studied while the oil-soluble agent added in theirinner oil phase was changed.

(1) Composition

                  TABLE 41                                                        ______________________________________                                                                   Comp.    Comp.                                                       Ex. 7    Ex. 7    Ex. 8                                     Constituent       (O/W/O)  (W/O)    (W/O)                                     ______________________________________                                        (a) Surfactant phase                                                          1,3-Butyleneglycol                                                                              5        5        5                                         POE(60) hardened castor oil                                                                     1        --       --                                        Methyl paraben    0.1      0.1      0.1                                       (b) Inner oil phase                                                           Squalane          5        --       --                                        Pentaerythritol   5        --       --                                        tetra-2-ethylhexanoate                                                        Ultraviolet absorber(cf. Table 42)                                                              2        --       --                                        (c) Water phase                                                               Purified water    48.9     59.9     59.9                                      (d) Outer oil phase                                                           Dioctyl succinate 9        9        30                                        Dimethylpolysiloxane                                                                            10       10       --                                        Decamethylcyclopentasiloxane                                                                    10       10       --                                        Silicone gum      1        1        --                                        Organophilic clay mineral                                                                       1        1        1                                         (Preparation 1)                                                               POE(6) stearyl ether                                                                            1        1        1                                         POE methylpolysiloxane copolymer*                                                               1        1        1                                         Ultraviolet absorber(cf. Table 42)                                                              --       2        2                                         ______________________________________                                         *The product name is Silicone SC9450N(manufactured by SINETSU KAGAKU KOGY     Co., Ltd.).                                                              

(2) Method of preparation

EXAMPLE 12

It was prepared in a manner similar to Example 6.

COMPARATIVE EXAMPLE 7 AND 8

It was prepared in a manner similar to Comparative Example 2.

(3) Method of evaluation

With respect to the emulsions shown in Table 41, observation of theemulsified state was performed by the above-mentioned method, wherebychanges in emulsification conditions such as change in particle size,separation, and discoloring were inspected so as to evaluate theemulsification stability. Here, the storage period was six months at 25°C. or two months at 50° C. Also, effect of prevention of the crystaldeposit and the feel of use were evaluated by the above-mentionedmethod.

(4) Result

                                      TABLE 42                                    __________________________________________________________________________    Emulsification Stability                                                                          Emulsification                                                                        Crystal                                                                             Feel                                        Ultraviolet absorber                                                                              stability                                                                             deposit                                                                             of use                                      __________________________________________________________________________    Example (O/W/O)                                                               12-1                                                                              2,4-dihydroxybenzophenone                                                                     ⊚                                                                      ◯(none)                                                                 ⊚                            12-2                                                                              2,2'-dihydroxy-4-methoxy                                                                      ⊚                                                                      ◯(none)                                                                 ⊚                                benzophenone                                                              12-3                                                                              2,2'-dihydroxy-4,4-dimethoxy                                                                  ⊚                                                                      ◯(none)                                                                 ⊚                                benzophenone                                                              12-4                                                                              2,2',4,4'-tetrahydroxybenzophenone                                                            ⊚                                                                      ◯(none)                                                                 ⊚                            12-5                                                                              2-hydroxy-4-methoxy                                                                           ⊚                                                                      ◯(none)                                                                 ⊚                                benzophenone                                                              12-6                                                                              2-hydroxy-4-methoxy-4'-methyl                                                                 ⊚                                                                      ◯(none)                                                                 ⊚                                benzophenone                                                              12-7                                                                              3-(4-methylbenzylidene)-d,1-camphor                                                           ⊚                                                                      ◯(none)                                                                 ⊚                            12-8                                                                              3-benzylidene-d,1-campohor                                                                    ⊚                                                                      ◯(none)                                                                 ⊚                            12-9                                                                              4-methoxy-4'-t-butyl                                                                          ⊚                                                                      ◯(none)                                                                 ⊚                                dibenzoylmethane                                                          __________________________________________________________________________    Comparative Example (W/O, containing a silicone type oil)                      7-1                                                                              2,4-dihydroxybenzophenone                                                                     X       X(deposit)                                                                          ◯                                7-2                                                                              2,2'-dihydroxy-4-methoxy                                                                      X       X(deposit)                                                                          ◯                                   benzophenone                                                               7-3                                                                              2,2'-dihydroxy-4,4-dimethoxy                                                                  X       X(deposit)                                                                          ◯                                   benzophenone                                                               7-4                                                                              2,2',4,4'-tetrahydroxybenzophenone                                                            X       X(deposit)                                                                          ◯                                7-5                                                                              2-hydroxy-4-methoxy                                                                           X       X(deposit)                                                                          ◯                                   benzophenone                                                               7-6                                                                              2-hydroxy-4-methoxy-4'-methyl                                                                 X       X(deposit)                                                                          ◯                                   benzophenone                                                               7-7                                                                              3-(4-methylbenzylidene)-d,1-camphor                                                           X       X(deposit)                                                                          ◯                                7-8                                                                              3-benzylidene-d,1-campohor                                                                    X       X(deposit)                                                                          ◯                                7-9                                                                              4-methoxy-4'-t-butyl                                                                          X       X(deposit)                                                                          ◯                                   dibenzoylmethane                                                          __________________________________________________________________________    Comparative Example (W/O, containing no silicone type oils)                    8-1                                                                              2,4-dihydroxybenzophenone                                                                     X       ◯(none)                                                                 X                                            8-2                                                                              2,2'-dihydroxy-4-methoxy                                                                      X       ◯(none)                                                                 X                                               benzophenone                                                               8-3                                                                              2,2'-dihydroxy-4,4-dimethoxy                                                                  X       ◯(none)                                                                 X                                               benzophenone                                                               8-4                                                                              2,2',4,4'-tetrahydroxybenzophenone                                                            X       ◯(none)                                                                 X                                            8-5                                                                              2-hydroxy-4-methoxy                                                                           X       ◯(none)                                                                 X                                               benzophenone                                                               8-6                                                                              2-hydroxy-4-methoxy-4'-methyl                                                                 X       ◯(none)                                                                 X                                               benzophenone                                                               8-7                                                                              3-(4-methylbenzylidene)-d,1-camphor                                                           X       ◯(none)                                                                 X                                            8-8                                                                              3-benzylidene-d,1-campohor                                                                    X       ◯(none)                                                                 X                                            8-9                                                                              4-methoxy-4'-t-butyl                                                                          X       ◯(none)                                                                 X                                               dibenzoylmethane                                                          __________________________________________________________________________

As can be seen from Table 42, though the W/O type emulsion ofComparative Example 7, in which a silicone type oil had been added inthe outer oil phase together with an ultraviolet absorber, wasrelatively favorable in terms of lack of greasiness; deposition of theultraviolet absorber was observed therein during storage since theultraviolet absorber was added in the same oil phase as the siliconetype oil in which the absorber had a low solubility.

On the other hand, in the case of the W/O type emulsion such asComparative Example 8 in which a polar oil content, to which theultraviolet absorber was highly soluble, had been added in the outer oilphase in place of silicone type oil, there was greasiness though nodeposition of the ultraviolet absorber was observed over time, therebydeteriorating the feel of use.

Contrary to this, in the O/W/O type multiple emulsion of the presentinvention (Example 12-1 to 12-9), the crystal did not deposited and theemulsification stability was also good. Further, its feel of use hasrefreshness and lack of greasiness so that a cream having a good feel ofuse as compared with that of the emulsion of Comparative Example 5 couldbe obtained.

As explained in the foregoing, in the multiple emulsion of the presentinvention, while the components which were hard to dissolve each other,such as the agent having slight-solubility to silicone type oils,non-silicone type oils, and silicone type oils, coexist in one emulsionsystem, the crystal of the agent can be prevented from depositing and amultiple emulsion having very good stability of emulsification and feelof use can be obtained. Therefor, it is possible to prepare a suncarecosmetics or the like having very good feel of use and stability.

EXAMPLE 13

In O/W/O type multiple emulsions containing a silicone type oil, usingan oil-soluble vitamin(vitamin A palmitate) and an oil-solubleultraviolet absorber(octyl dimethyl PABA), which are easily oxidized, asan oil-soluble agent, O/W/O type multiple emulsions were prepared in amanner similar to the preparation method of the above-mentioned Example6, while the amounts of the respective ingredients were changedaccording to the prescriptions shown in Tables 43 and 44. As a result,it was evidenced that, as in the case of Table 20, the system hasfavorable emulsification stability and agent stability to oxidation evenwhen the ratio of O/W type emulsion to outer oil phase is within therange of 2:3 to 19:1 by weight ratio.

                  TABLE 43                                                        ______________________________________                                        Study of Composition Ratio                                                                    Example                                                       Constituent       13-1   13-2   13-3 13-4 13-5                                ______________________________________                                        (a) Surfactant                                                                1,3-Butyleneglycol                                                                              5      5      5    5    5                                   Glycerine         2      2      2    2    2                                   POE(60) hardened castor oil                                                                     1      1      1    1    1                                   Methyl paraben    0.1    0.1    0.1  0.1  0.1                                 (b) Inner oil phase                                                           Squalane          5      5      5    5    5                                   Vitamin A palmitate                                                                             0.2    0.2    0.2  0.2  0.2                                 (c) Water phase                                                               Purified water    82.2   76.7   56.7 36.7 16.7                                (d) Outer oil phase                                                           Octamethylcyclotetrasiloxane                                                                    2.1    7.6    27.6 47.6 67.6                                Cationic denatured clay mineral                                                                 2      2      2    2    2                                   (Benton-38)                                                                   POE methylpolysiloxane copolymer*                                                               0.4    0.4    0.4  0.4  0.4                                 O/W emulsion:outer oil phase                                                                    21:1   9:1    7:3  5:5  3:7                                 (weight ratio)                                                                Emulsification stability                                                      (observation of the state)                                                    50° C.     X      ◯                                                                        ⊚                                                                   ◯                                                                      X                                   Remaining ratio of vitamin                                                                      X      ⊚                                                                     ⊚                                                                   ⊚                                                                   X                                   A palmitate                                                                   ______________________________________                                         *The product name is Silicone SC9450N(manufactured by SINETSU KAGAKU KOGY     Co., Ltd.).                                                              

                  TABLE 44                                                        ______________________________________                                        Study of Composition Ratio                                                                    Example                                                       Constituent       13-6   13-7   13-8 13-9 13-10                               ______________________________________                                        (a) Surfactant                                                                1,3-Butyleneglycol                                                                              5      5      5    5    5                                   Glycerine         2      2      2    2    2                                   POE(60) hardened castor oil                                                                     1      1      1    1    1                                   Methyl paraben    0.1    0.1    0.1  0.1  0.1                                 (b) Inner oil phase                                                           Octyl methoxycinnamate                                                                          5      5      5    5    5                                   Glyceryl tri-2-ethylhexanoate                                                                   10     10     10   10   10                                  Octyl dimethyl PABA**                                                                           1      1      1    1    1                                   (c) Water phase                                                               Purified water    70.75  65.3   45.3 25.3 5.3                                 (d) Outer oil phase                                                           Liquid paraffin   0.65   2.6    9.2  16.0 22.6                                Decamethylcyclopentasiloxane                                                                    1.5    5.0    18.4 31.6 45.0                                Cationic denatured clay mineral                                                                 1      1      1    1    1                                   (Benton-38)                                                                   POE(10) sorbitan fatty acid ester                                                               1      1      1    1    1                                   POE methylpolysiloxane copolymer*                                                               1      1      1    1    1                                   O/W emulsion:outer oil phase                                                                    21:1   5:1    2:1  1:1  0.5:1                               (weight ratio)                                                                Emulsification stability                                                      (observation of the state)                                                    50° C.     X      ◯                                                                        ⊚                                                                   ◯                                                                      X                                   Remaining ratio   X      ⊚                                                                     ⊚                                                                   ⊚                                                                   X                                   of Octyl dimethyl PABA                                                        ______________________________________                                         *The product name is Silicone SC9450N(manufactured by SINETSU KAGAKU KOGY     CO., Ltd.).                                                                   **Octyl dimethyl PABA; Octyl pdimethylaminobenzoate.                     

EXAMPLE 14 AND COMPARATIVE EXAMPLE 9 TO 10

Further, in O/W/O type multiple emulsions containing a silicone typeoil, agent remaining ratio was studied when various oil-soluble vitaminswere added in the inner oil phase as a agent which were easily oxidized.

(1) Composition

                  TABLE 45                                                        ______________________________________                                                                   Comp.    Comp.                                                       Ex. 14   Ex. 9    Ex. 10                                    Constituent       (O/W/O)  (W/O)    (O/W/O)                                   ______________________________________                                        (a) Surfactant phase                                                          1,3-Butyleneglycol                                                                              5        5        5                                         POE(60) hardened castor oil                                                                     1        --       --                                        Bentonite         --       --       0.5                                       Methyl paraben    0.1      0.1      0.1                                       (b) Inner oil phase                                                           Squalane          5        --       5                                         Pentaerythritol   5        --       5                                         tetra-2-ethylhexanoate                                                        Cetanol           --       --       3                                         POE(20) sorbitan tristearate                                                                    --       --       1                                         Diglycerine monooleate                                                                          --       --       2                                         Oil-soluble vitamin(cf. Table 46)                                                               1        --       1                                         (c) Water phase                                                               Purified water    51.9     52.9     37.4                                      (d) Outer oil phase                                                           Liquid paraffin   10       10       10                                        Dimethylpolysiloxane                                                                            10       10       10                                        Decamethylcyclopentasiloxane                                                                    10       10       10                                        Organophilic clay mineral                                                                       1        1        1                                         (Preparation 1)                                                               Squalene          --       5        --                                        Pentaerythritol   --       5        --                                        tetra-2-ethylhexanoate                                                        Dextrin palmitate --       --       1                                         Cetanol           --       --       3                                         Beeswax           --       --       2                                         Sorbitan sesquioleate                                                                           --       --       3                                         Sorbitan monostearate                                                                           --       --       1                                         Oil-soluble vitamin(cf. Table 46)                                                               --       1        --                                        ______________________________________                                    

(2) Method of Preparation

EXAMPLE 6

It was prepared in a manner similar to Example 6.

COMPARATIVE EXAMPLE 2

It was prepared in a manner similar to Comparative Example 2.

COMPARATIVE EXAMPLE 3

It was prepared in a manner similar to Comparative Example 3.

(3) Method of Evaluation

The emulsification stability and agent remaining ratio of thus preparedemulsion were evaluated in the above-mentioned manner. Also, discoloringand change in odor of the emulsion after being kept at 50° C. in anincubator for one month were judged in a manner similar to Example 6.

(4) Result

                                      TABLE 46                                    __________________________________________________________________________    Evaluation of Emulsion Characteristics                                                          Emulsification stability                                                                   Remaining ratio                                Example  Oil-soluble vitamin                                                                    Discoloring                                                                         Odor                                                                             State                                                                             of Vitamin(%)                                  __________________________________________________________________________    Example                                                                            14-1                                                                              retinol  ⊚                                                                    ⊚                                                                 ◯                                                                     90.1                                           (O/W/O)                                                                            14-2                                                                              vitamin A palmitate                                                                    ⊚                                                                    ⊚                                                                 ◯                                                                     97.5                                                14-3                                                                              vitamin A acetate                                                                      ⊚                                                                    ⊚                                                                 ◯                                                                     95.1                                                14-4                                                                              α-tocopherol                                                                     ⊚                                                                    ⊚                                                                 ◯                                                                     92.2                                                14-5                                                                              vitamin E acetate                                                                      ⊚                                                                    ⊚                                                                 ◯                                                                     99.8                                                14-6                                                                              vitamin D.sub.2                                                                        ⊚                                                                    ⊚                                                                 ◯                                                                     93.2                                                14-7                                                                              β-carotene                                                                        ⊚                                                                    ⊚                                                                 ◯                                                                     99.1                                           __________________________________________________________________________    Comp. Ex.                                                                           9-1                                                                              retinol  X     X  ◯                                                                     48.9                                           (W/O)                                                                               9-2                                                                              vitamin A palmitate                                                                    Δ                                                                             Δ                                                                          ◯                                                                     67.5                                                 9-3                                                                              vitamin Acetate                                                                        Δ                                                                             Δ                                                                          ◯                                                                     50.8                                                 9-4                                                                              α-tocopherol                                                                     Δ                                                                             ◯                                                                    ◯                                                                     63.2                                                 9-5                                                                              vitamin E acetate                                                                      ◯                                                                       ◯                                                                    ◯                                                                     70.4                                                 9-6                                                                              vitamin D.sub.2                                                                        Δ                                                                             ◯                                                                    ◯                                                                     83.3                                                 9-7                                                                              β-carotene                                                                        Δ                                                                             ◯                                                                    ◯                                                                     87.1                                           __________________________________________________________________________    Comp. Ex.                                                                          10-1                                                                              retinol  X     X  X   12.2                                           (O/W/O)                                                                            10-2                                                                              vitamin A palmitate                                                                    X     X  X   22.3                                                10-3                                                                              vitamin A acetate                                                                      X     X  X   30.6                                                10-4                                                                              α-tocopherol                                                                     Δ                                                                             Δ                                                                          X   63.7                                                10-5                                                                              vitamin E acetate                                                                      Δ                                                                             Δ                                                                          X   72.4                                                10-6                                                                              vitamin D.sub.2                                                                        Δ                                                                             Δ                                                                          X   77.7                                                10-7                                                                              β-carotene                                                                        Δ                                                                             ◯                                                                    Δ                                                                           69.6                                           __________________________________________________________________________

As can be seen from Table 46, the O/W/O type emulsions (Examples 14-1 to14-7) were excellent in emulsification stability without separation ofoil or the like, discoloring, and change in odor and exhibited aremarkably high agent remaining ratio.

EXAMPLE 15

Next, the multiple emulsion of the present invention in which ahydrophilic polymer was added has been studied.

                  TABLE 47                                                        ______________________________________                                        O/W Type Emulsion                                                                                    Example                                                Constituent            15-1                                                   ______________________________________                                        (a) Surfactant phase                                                          1,3-Butanediol         21                                                     Purified water          2                                                     POE(60) hardened castor oil                                                                           2                                                     (b) Oil phase                                                                 Liquid paraffin        33                                                     (c) Water phase                                                               Purified water         39                                                     Sodium alginate         3                                                     Emulsification stability                                                      (observation of the state)                                                    RT                     ◯                                          50° C.          ◯                                          ______________________________________                                    

<Method of Preparation>

In a manner similar to the method of Table 3 of Example 1 shown above,the O/W type emulsion was prepared. 1 g of 10% aqueous calcium chloridesolution was added with respect to 100 g of thus obtained emulsion,thereby making sodium alginate gel.

                  TABLE 48                                                        ______________________________________                                        W/O Type Emulsion                                                                          Example                                                          Constituent    15-2   15-3   15-4 15-5 15-6 15-7                              ______________________________________                                        (a) Surfactant                                                                POE(3) oleyl ether                                                                            1     --     --   --   --   --                                POE(2) oleyl ether                                                                           --      5     --   --   --   --                                Sorbitan monostearate                                                                        --     --      1   --   --   --                                Sorbitan monostearate                                                                        --     --     --    5   --   --                                POE(10) hardened castor oil                                                                  --     --     --   --   10   --                                POE(10) hardened castor oil                                                                  --     --     --   --   --    5                                (b) Oil phase                                                                 Liquid paraffin                                                                              39     35     39   35   30   35                                (c) Water phase                                                               Ion-exchanged water                                                                          57     57     57   57   57   57                                Sodium alginate                                                                               3      3      3    3    3    3                                Emulsification stability                                                      (observation of the state)                                                    RT             ◯                                                                        ◯                                                                        ◯                                                                      ◯                                                                      ◯                                                                      ◯                     50° C.  ◯                                                                        ◯                                                                        ◯                                                                      ◯                                                                      ◯                                                                      ◯                     ______________________________________                                    

<Method of Preparation>

In a manner similar to the method of Table 4 of Example 1 shown above,the W/O type emulsion was prepared. 1 g of 10% aqueous calcium chloridesolution was added with respect to 100 g of thus obtained emulsion,thereby making sodium alginate gel.

                  TABLE 49                                                        ______________________________________                                        O/W/O Type Emulsion                                                                        Example                                                          Constituent    15-8   15-9   15-10                                                                              15-11                                                                              15-12                                                                              15-13                             ______________________________________                                        (a) O/W phase (containing                                                     sodium alginate in the water                                                  phase)                                                                        O/W type emulsion of                                                                         70     70     70   70   70   70                                Example 15-1                                                                  (b) Outer oil phase                                                           Liquid paraffin                                                                              29     25     29   25   20   25                                (c) Lipophilic surfactant                                                     POE(3) oleyl ether                                                                            1     --     --   --   --   --                                POE(2) oleyl ether                                                                           --      5     --   --   --   --                                Sorbitan monostearate                                                                        --     --      1   --   --   --                                Sorbitan monostearate                                                                        --     --     --    5   --   --                                POE(10) hardened castor oil                                                                  --     --     --   --   10   --                                POE(10) hardened castor oil                                                                  --     --     --   --   --    5                                Emulsification stability                                                      Observation of the state                                                      RT             X      X      X    X    X    X                                 50° C.  X      X      X    X    X    X                                 Inner oil phase remaining                                                                    <5     <5     <5   <5   <5   <5                                ratio (after 8 weeks at 50° C.)                                        ______________________________________                                    

<Method of Preparation>

In a manner similar to the method of Table 5 of Example 1 shown above,the O/W type emulsion was prepared. 1 g of 10% aqueous calcium chloridesolution was added with respect to 100 g of thus obtained emulsion,thereby making sodium alginate gel.

                  TABLE 50                                                        ______________________________________                                        O/W/O Type Emulsion                                                                           Example                                                       Constituent       15-14  15-15  15-16                                                                              15-17                                                                              15-18                               ______________________________________                                        (a) O/W phase(containing sodium                                               alginate in the water phase)                                                  O/W type emulsion 70     70     70   70   70                                  of Example 15-1                                                               (b) Outer oil phase                                                           Liquid paraffin   28     28     28   28   28                                  (c) Surfactant in outer oil phase                                             Organophilic clay mineral                                                                        2     --     --   --   --                                  (Preparation 1)                                                               Unmodified clay mineral(Beegum)                                                                 --      2     --   --   --                                  Benzyldimethylstearyl ammonium                                                                  --     --      2   --   --                                  chloride                                                                      POE(6)lauryl ether                                                                              --     --     --    2   --                                  Benzyldimethylstearyl ammonium                                                                  --     --     --   --    2                                  chloride + POE(6)                                                             lauryl ether                                                                  Emulsification stability                                                      Observation of the state                                                      RT                ◯                                                                        X      X    X    X                                   50° C.     ◯                                                                        X      X    X    X                                   Inner oil phase remaining ratio                                                                 98     <5     <5   <5   <5                                  (after 8 weeks at 50° C.)                                              ______________________________________                                    

<Method of Preparation>

In a manner similar to the method of Table 6 of Example 1 shown above,the O/W type emulsion was prepared. 1 g of 10% aqueous calcium chloridesolution was added with respect to 100 g of thus obtained emulsion,thereby making sodium alginate gel.

According to Tables 47 and 48, a considerably high emulsificationstability can be attained in O/W type emulsions and W/O type emulsionsby selecting appropriate surfactants. However, when a stable O/Wemulsion was dispersed in the outer oil phase to form an O/W/O typeemulsion, the emulsification stability of thus obtained O/W/O emulsionwas greatly deteriorated, whereby the inner oil phase exuded into theouter oil phase.

Also, as can be seen from Table 49, even when hydrophilic polymer whichis commonly effective to stabilize emulsification state is added in thewater phase of O/W/O type multiple emulsion, its stability cannot beimproved greatly.

Contrary to this, as shown in Table 50, even in the case where ahydrophilic polymer is added in the water phase, when an organophilicclay mineral is added in the outer oil phase, the emulsificationstability is very good in terms of observation of emulsified state andinner oil phase remaining ratio, thereby yielding an excellent effect ofemulsification stabilization.

Accordingly, the emulsification stability of the multiple emulsioncannot be improved when the stable O/W type emulsion is simplysubstituted for a water phase of the stable W/O type emulsion, eventhough a hydrophilic polymer is added in the water phase to be made togel. The effect on the stability of the multiple emulsion can beobtained specifically by adding the organophilic clay mineral.

EXAMPLE 16

A preferable composition of the multiple emulsion of the presentinvention was studied in the case adding a hydrophilic polymer in thewater phase.

(1) Composition

                  TABLE 51                                                        ______________________________________                                        Composition of O/W Type Emulsion                                              Constituent            Content                                                ______________________________________                                        (a) Surfactant phase                                                          1,3-Butanediol         21                                                     Purified water          2                                                     POE(60) hardened castor oil                                                                           2                                                     (b) Inner oil phase                                                           Liquid paraffin        33                                                     (c) Water phase                                                               Purified water         39                                                     Sodium alginate         3                                                     ______________________________________                                    

                  TABLE 52                                                        ______________________________________                                        Composition of Outer oil phase                                                Constituent            Content                                                ______________________________________                                        (d) Surfactant                                                                Organophilic clay mineral                                                                             7                                                     of Preparation 1                                                              (e) Outer phase oil                                                           Liquid paraffin        93                                                     ______________________________________                                    

                  TABLE 53                                                        ______________________________________                                        Constitutional Ratio of O/W/O Type Multiple Emulsion                                     Amount of O/W                                                                 type emulsion                                                                             Amount of outer oil phase                              Example    (parts by weight)                                                                         (parts by weight)                                      ______________________________________                                        Example 16-1                                                                             50          50                                                     Example 16-2                                                                             60          40                                                     Example 16-3                                                                             70          30                                                     Example 16-4                                                                             80          20                                                     Example 16-5                                                                             35          65                                                     Example 16-6                                                                             97           3                                                     ______________________________________                                    

(2) Method of preparation

First, into the mixture of uniformly dissolved ingredient (a) shown inTable 51, ingredient (b) was mixed and emulsified while being stirred.Then, ingredient (c) was added thereto and mixed therewith to yield anO/W type emulsion.

Thereafter, the outer oil phase component shown in Table 52 was mixed.In this outer oil phase, the O/W type emulsion prepared above was mixedand emulsified while being stirred to yield the aimed O/W/O typemultiple emulsion and then 1 g of 10% aqueous calcium chloride solutionwas added with respect to 100 g of thus obtained emulsion to make sodiumalginate gel, thereby yielding aimed multiple emulsion. Here, the ratioof the O/W type emulsion to the outer oil phase was changed as shown inTable 53 to form Examples 16-1 to 16-6.

(3) Result

                  TABLE 54                                                        ______________________________________                                        Evaluation of Emulsion Characteristics                                                             Emulsifi-                                                          Emulsion form                                                                            cation     Inner oil phase                                         directly after                                                                           stability  remaining ratio*                              Outer oil phase                                                                         preparation                                                                              RT     50° C.                                                                       (50° C., 1 month)                    ______________________________________                                        Ex. 16-1  O/W/O      ◯                                                                        ◯                                                                       93.0%                                       Ex. 16-2  O/W/O      ⊚                                                                     ◯                                                                       95.5                                        Ex. 16-3  O/W/O      ⊚                                                                     ⊚                                                                    98.6                                        Ex. 16-4  O/W/O      ⊚                                                                     ◯                                                                       92.8                                        Ex. 16-5  O/W/O      X      X     --                                          Ex. 16-6  O/W/O + O/W                                                                              X      X     --                                          ______________________________________                                    

As can be seen from Table 54, in the multiple emulsion of the presentinvention, even when a hydrophilic polymer is added in the water phase,the preferable ratio of O/W type emulsion to the outer oil phase iswithin the range of 2:3 to 19:1.

COMPARATIVE EXAMPLE 11

Outer oil phases were prepared according to compositions in thefollowing Table 55 to form Comparative Examples 11-1 to 11-6. In eachouter oil phase, the lipophilic surfactant commonly used for preparingthe conventional W/O type emulsion was used therein.

Further, an O/W type emulsion prepared in a manner similar to Table 51of Example 16 and each of the outer oil phases of Comparative Examplesshown in Table 55 were mixed and emulsified together at a ratio of 7:3by weight and then 1 g of 10% aqueous calcium chloride solution wasadded with respect to 100 g of thus obtained emulsion to make sodiumalginate gel, thereby yielding aimed O/W/O type multiple emulsion.

The emulsification stability of thus prepared emulsion is shown in Table56.

                  TABLE 55                                                        ______________________________________                                        Composition of Outer Oil Phase                                                          Lipophilic surfactant                                                                            Oil                                              Outer oil phase                                                                         (parts by weight)  (parts by weight)                                ______________________________________                                        Comp. Ex. 11-1                                                                          POE(3)oleyl ether (1)                                                                            liquid paraffin                                                               (99)                                             Comp. Ex. 11-2                                                                          POE(3)oleyl ether (5)                                                                            liquid paraffin                                                               (95)                                             Comp. Ex. 11-3                                                                          sorbitan monostearate (1)                                                                        liquid paraffin                                                               (99)                                             Comp. Ex. 11-4                                                                          sorbitan monostearate (5)                                                                        liquid paraffin                                                               (95)                                             Comp. Ex. 11-5                                                                          POE(10) hardened castor oil (10)                                                                 liquid paraffin                                                               (90)                                             Comp. Ex. 11-6                                                                          POE(10) hardened castor oil (5)                                                                  liquid paraffin                                                               (95)                                             ______________________________________                                    

                  TABLE 56                                                        ______________________________________                                        Evaluation of Emulsion Characteristics                                                                 Emulsion                                                       Emulsion form  stability                                            Outer oil phase                                                                           directly after preparation                                                                     RT    50° C.                              ______________________________________                                        Comp. Ex. 11-1                                                                            O/W/O            X     X                                          Comp. Ex. 11-2                                                                            O/W/O + O/W      X     X                                          Comp. Ex. 11-3                                                                            O/W/O            X     X                                          Comp. Ex. 11-4                                                                            O/W/O            X     X                                          Comp. Ex. 11-5                                                                            O/W/O + O/W      X     X                                          Comp. Ex. 11-6                                                                            O/W/O + O/W      X     X                                          ______________________________________                                    

When the evaluation in Table 54 and that of in Table 56 are comparedwith each other, it can be seen that Examples 16-1 to 16-4 of thepresent invention are superior in emulsification stability toComparative Examples 11-1 to 11-6.

EXAMPLE 17 AND COMPARATIVE EXAMPLE 12

As explained in the following, effects of the multiple emulsioncontaining a hydrophilic polymer added therein when applied on skin wereevaluated in terms of skin irritation and continuance of the effects.

Namely, while the hydrophilic polymer added to the water phase iseffective in stabilizing the composition, particular effects are seen ingradually releasing the medically active components in the inner oilphase. According to this gradual releasing, the agent can be preventedfrom acutely acting on the skin, while the effects of the agent can becontinued.

Here, specifically, the samples having compositions of the followingTable 57 were applied to the upper arms of a panel consisting of 25 eachof males and females, and irritation such as stingingness was evaluated30 minutes after the application, whereas the continuance of effects wasevaluated three hours after the application. Each judgement standard wasas follows;

Irritation to Skin

⊚: Among 50 panels, 0 to 5 panels felt stingingness to skin.

O: Among 50 panels, 6 to 20 panels felt stingingness to skin.

Δ: Among 50 panels, 21 to 35 panels felt stingingness to skin.

X: Among 50 panels, 36 to 50 panels felt stingingness to skin.

Continuance of Effects

⊚: Among 50 panels, 36 to 50 panels felt continuance of effects.

O: Among 50 panels, 21 to 35 panels felt continuance of effects.

Δ: Among 50 panels, 6 to 20 panels felt continuance of effects.

X: Among 50 panels, 0 to 5 panels felt continuance of effects.

                                      TABLE 57                                    __________________________________________________________________________                    Example   Comp. Ex.                                           Constituent     17-1 17-2 12-1                                                                              12-2                                                                              12-3                                        __________________________________________________________________________    Emulsification Form                                                                           O/W/O                                                                              O/W/O                                                                              O/W W/O O/W/O                                       (a)                                                                           1,3-Butyleneglycol                                                                            10.5 --    10.5                                                                             10.5                                                                              --                                          Purified water  1    --   1   --  --                                          POE(60) hardened castor oil                                                                   1    --   1   --  --                                          POE(25) cetyl ether                                                                           --   3    --  --  --                                          Glyceryl monostearate                                                                         --   2    --  --  --                                          (a')                                                                          Glycerine       --   5    --  --  5                                           Bentonite       --   --   --  --  0.5                                         (b)                                                                           Liquid paraffin 15.4 9    28.9                                                                              26.9                                                                              14.4                                        POE(20) sorbitan tristearate                                                                  --   --   --  --  1                                           Glyceryl trioctanoate                                                                         --   3    --  --  --                                          Olive oil       --   2    --  --  --                                          Stearyl alchol  --   0.5  --  --  --                                          (c)                                                                           nonylic acid vanillic acid nonylamide                                                         1    1    1   1   1                                           (d)                                                                           Purified water  TO 100                                                        (e)                                                                           Organophilic clay mineral                                                                     2    2    --  2   1                                           (Preparation 2)                                                               (e')                                                                          Dextrin stearate                                                                              --   --   --  --  1                                           (f)                                                                           Liquid paraffin 28   28   --  --  29                                          (g)                                                                           Cardrant        1    1    --  --  --                                          (h)                                                                           Kertrol         --   --   1   --  --                                          (i)                                                                           1N--NaOH        0.2  0.2  --  --  --                                          (j)                                                                           1N--HCl         0.2  0.2  --  --  --                                          Irritation to skin (Stingingness)                                                             ⊚                                                                   ◯                                                                      Δ                                                                           X   ◯                               Continuance of effects                                                                        ⊚                                                                   ◯                                                                      X   X   Δ                                     __________________________________________________________________________

As shown in Table 57, in the O/W/O multiple emulsion in accordance withthe present invention, as compared with the other simple emulsionsystem, low irritation to skin and continuance of effects could beobtained. Also, the O/W/O type multiple emulsion prepared by ComparativeExample 12-3 could not exhibit a enough effect in gradually releasingthe drug because it did not contain a hydrophilic polymer in the waterphase.

Here, the method of preparing each composition is as follows;

EXAMPLE 17-1

After ingredient (a) and ingredient (b)+(c) were separately melted to beuniform, ingredient (b)+(c) was mixed and emulsified in ingredient (a)while being stirred and then ingredient (d)+(g)+(i) was added thereto,thereby preparing an O/W type emulsion. While being stirred, thusobtained O/W type emulsion was mixed and emulsified in ingredient(e)+(f), which had been mixed beforehand, and then ingredient (j) wasadded thereto, thereby yielding the aimed O/W/O type multiple emulsion.

EXAMPLE 17-2

After ingredient (a)+(b)+(c) and ingredient (a')+(d) were separatelymelted to be uniform, by using the phase inversion method as it wascalled, (a')+(d) was mixed and emulsified in ingredient (a)+(b)+(c)while being stirred, thereby yielding an O/W type emulsion. Intoingredient (g) suspended in a small amount of purified water, ingredient(i) was added and dissolved therein, thereby yielding an O/W typeemulsion containing cardrant. While being stirred, thus obtained O/Wtype emulsion containing cardrant was mixed and emulsified in ingredient(e)+(f), which had been mixed beforehand, and then ingredient (j) wasadded thereto, thereby yielding the aimed O/W/O type multiple emulsion.

COMPARATIVE EXAMPLE 12-1

Into ingredient (a) uniformly mixed and dissolved, ingredient (b)+(c)was mixed and emulsified therein while being stirred. Ingredients (d)and ingredient (h) were admixed thereto, thereby yielding the aimed O/Wtype emulsion.

EXAMPLE 12-2

After ingredient (b)+(c)+(e) was uniformly mixed and dissolved whilebeing stirred, ingredient (a)+(d) was mixed and emulsified therein whilebeing stirred, thereby yielding the aimed W/O type emulsion.

COMPARATIVE EXAMPLE 12-3

After ingredient (a')+(d) and ingredient (b)+(c) were separately heatedand melted, ingredient (b)+(c) was mixed, dispersed, and emulsified iningredient (a')+(d) while being stirred, thereby yielding an O/W typeemulsion. Then, this O/W type emulsion was mixed in ingredient (e')+(f),which had been heated and mixed at 80° C. beforehand, and then cooled to30° C. while being stirred, thereby yielding the aimed O/W/O typemultiple emulsion.

EXAMPLE 18 AND COMPARATIVE EXAMPLE 13

Next, emulsions were prepared in a manner similar to Table 57 shownabove except for using methyl salicylate in stead of nonyl vanillic acidnonylamide and their evaluation had been performed. The result was shownin Table 58 below.

                                      TABLE 58                                    __________________________________________________________________________                    Example   Comp. Ex.                                           Constituent     18-1 18-2 13-1                                                                              13-2                                                                              13-3                                        __________________________________________________________________________    Irritation to skin (Stingingness)                                                             ⊚                                                                   ◯                                                                      Δ                                                                           Δ                                                                           Δ                                     Continuance of effects                                                                        ⊚                                                                   ◯                                                                      X   X   Δ                                     __________________________________________________________________________

As shown in Table 58, in the multiple emulsion in accordance with thepresent invention, excellent effect of decreasing irritation to skin andcontinuance of effect of the drug could be obtained.

As explained in the foregoing, in the multiple emulsion and method ofpreparing the same in accordance with the present invention, thefollowing advantageous effects can be obtained:

(1) Since a stable and uniform multiple emulsion can be obtained easilyat normal temperature without necessitating any special emulsifier or aheating and rapid cooling step, its manufacturing cost becomes low.

(2) Since a stable and uniform multiple emulsion can be obtained easilyat normal temperature without necessitating a heating and rapid coolingstep, a thermally unstable ingredient can be stably compounded therein.

(3) A stable and uniform O/W/O type multiple emulsion can be obtainedand, when an oil-soluble agent is added in its inner oil phase, anexcellent agent stability can be obtained as well.

(4) When the water phase is made to gel by using a hydrophilic polymer,the drug dissolved in the inner oil phase can be released gradually,thereby yielding the effect on decreasing irritation and continuance ofthe effects of the drug.

What is claimed is:
 1. An oil-in-water-in-oil multiple emulsion comprising an oil-in-water emulsion dispersed in a continuous outer oil phase, wherein said outer oil phase contains an organophilic clay mineral, whereby said organophilic clay mineral is an inclusion compound which is formed by cation exchange reaction between a water swellable-clay mineral and a quaternary ammonium cation and by physical adsorption with a nonionic surfactant.
 2. A multiple emulsion as claimed in claim 1, wherein a blending ratio of the oil-in-water type emulsion to the outer oil phase is within a range of 2:3 to 19:1 by weight ratio.
 3. A multiple emulsion as claimed in claim 1, wherein a silicone type oil is contained in the oil phase.
 4. A multiple emulsion as claimed in claim 3, wherein the silicone type oil is contained in the outer oil phase.
 5. A multiple emulsion as claimed in claim 3, wherein the silicone type oil is within a range of 5 to 60 weight % with respect to a whole amount of the multiple emulsion.
 6. A multiple emulsion as claimed in claim 3, wherein the silicone type oil has a boiling point which is 200° C. or less.
 7. A multiple emulsion as claimed in claim 1, wherein an inner oil phase contains an oil-soluble material.
 8. A multiple emulsion as claimed in claim 7, wherein the oil-soluble material contained in the inner oil phase is slightly soluble in a silicone type oil and the silicone type oil is blended in the outer oil phase.
 9. A multiple emulsion as claimed in claim 7, wherein the oil-soluble material contained in the inner oil phase is one or more agent selected from the group consisting of oil-soluble vitamins, oil-soluble ultraviolet absorbers, and unsaturated fatty acids and the derivatives thereof which are easily oxidized.
 10. A multiple emulsion as claimed in claim 1, wherein a water phase contains a hydrophilic polymer.
 11. A multiple emulsion as claimed in claim 10, wherein the hydrophilic polymer is one or more selected from the group of sodium alginate, carrageenan, xanthan gum, gelatin, curdlan, agar, glucomannan, starch, hyaluronic acid, scleroglucan, schizophyllan, lentinan, paramylon, callose, laminaran, cellulose, methylcellulose, ethylcellulose, nitrocellulose, gum arabic, polyvinyl alcohol, carboxyvinyl polymer, carboxymethylcellulose, hydroxyethylcellulose, polyethylene glycol, tragacanth gum, garactan, guar gum, carob gum, karaya gum, pectin, guince seed, argecolloids, glycyrrhizinic acid, dextran, puluran, collagen, casein, albumen, carboxymethyl starch, methylhydroxypropyl starch, methylhydroxypropylcellulose, sodium cellulose sulfate, hydroxypropylcellulose, propylene glycol alginate, polyvinylmethyl ether, polyvinyl pyrrolidone, polyoxyethylene copolymer, sodium polyacrylate, polyethylacrylate, polyacryl amide, and polyethlene imine.
 12. The oil-in-water-in-oil type multiple emulsion according to claim 1, wherein said nonionic surfactant has an HLB value of more than 8 and less than
 16. 13. A method of preparing an oil-in-water-in oil multiple emulsion which comprises the steps of:preparing an oil in water-soluble solvent emulsion by blending components of an inner oil phase into a mixture of a hydrophilic nonionic surfactant and a water-soluble solvent; preparing an oil-in-water emulsion by blending components of a water phase into said oil in water-soluble solvent emulsion; and preparing an oil-in-water-in-oil multiple emulsion by dispersing and emulsifying said oil-in-water emulsion in a mixture of components of an outer oil phase which contains an organophilic clay mineral, whereby said organophilic clay mineral is an inclusion compound which is formed by cation exchange reaction between a water swellable-clay mineral and a quaternary ammonium cation and by physical adsorption with a nonionic surfactant.
 14. A method as claimed in claim 13, wherein a silicone type oil is contained in the oil phase.
 15. A method as claimed in claim 14, wherein the silicone type oil is contained in the outer oil phase.
 16. A method as claimed in claim 13, wherein the inner oil phase contains an oil-soluble material.
 17. A method as claimed in claim 16, wherein the oil-soluble material included in the inner oil phase is slightly soluble in a silicone type oil and the silicone type oil is contained in the outer oil phase.
 18. A method as claimed in claim 16, wherein the oil-soluble material contained in the inner oil phase is one or more agent selected from a group consisting of oil-soluble vitamins, oil-soluble ultraviolet absorbers, and unsaturated fatty acids and the derivatives thereof which are easily oxidized.
 19. A method as claimed in claim 13, which comprises the steps of:preparing an oil in water-soluble solvent emulsion by blending components of an inner oil phase into a mixture of a hydrophilic nonionic surfactant and a water-soluble solvent; preparing an oil-in-water emulsion by blending components of a water phase which contains water and a hydrophilic polymer into said oil in water-soluble solvent emulsion; preparing an oil-in-water-in-oil multiple emulsion by dispersing and emulsifying said oil-in-water emulsion in a mixture of components of an outer oil phase which contains an organophilic clay mineral, whereby said organophilic clay mineral is an inclusion compound which is formed by cation exchange reaction between a water swellable-clay mineral and a quaternary ammonium cation and by physical adsorption with a nonionic surfactant; and making a water phase gel by blending gelling agent of the hydrophilic polymer into said oil-in-water-in-oil multiple emulsion. 